A common, but little studied, feature of city walls and fortresses from late Antiquity and through the Middle Ages is the extent to which they often owed their structure, and sometimes their embellishment as well, to the re-use of materials originally cut for some other location or purpose.
The topic is of interest for several reasons.
1. It demonstrates new methods of construction, especially in reusing columns as tie bars (since classical tie-bars, when used at all, are metal cramps. The first build of Anavarza is indeed Roman, but unless what we now see in the lower levels is also Roman, I can find no examples of limestone or marble baulks in Antiquity used to tie walls together. Perhaps, therefore, the move away from metal cramps is a marker of new and less careful methods, and perhaps a fall-off of the necessary skills. Thus the Wall of Valerian in Athens (early 3rd century AD) uses cramps, whilst the Post-Herulian Wall (built after 267AD) does not . An indication that this technique had indeed fallen partly out of use in the Middle Ages is that, instead of being passed over as merely routine, it was received with marvel: on at least one occasion the huge blocks and tie-bars of a Roman wall were greeted with admiration in the Middle Ages, as in the dismantling of parts of the Wall of David at Jerusalem in 1239: les pierres estoient si granz que tuit s’en merveilloient. Elle estoit si fort maconee a chaux et ciment et a arainne, et les pierres soudeez a plomc et a grosses handes de fer acroschiez d’une part et d’autre que a trop grant painne et a trop grand force la porent ruer jus. So when Willbrand of Oldenburg visited Beirut in 1212 and noted the use of iron cramps in the walls and towers, was he looking at contemporary work, or classical work?
2. The use of spolia in military structures highlights the prestige with which military architecture was surrounded: lacking information about palaces, the only other types of buildings we know to have been decorated consistently with antiquities are churches, and palazzi pubblici in Italy. Embellishment with spolia may indicate that such architecture was conceived as performing much more than simply a protective function: rather, it served as a symbol of political as well as of military power.
3. Such reuse can be read, furthermore, as revealing a widespread and consistent respect for the antique past - especially in the most conspicious of its productions, namely architectural members, columns and reliefs - at a time when there was a dearth of contemporary productions to rival them.
4. The lavish use of spolia makes clear just what large quantities of material were available well into the second millennium after Christ - so that the mid-11th century Persian author Nasir-I-Hosran exclaims that Nella provincia di Siria la terra e seminata di piu che cinque centomila colonne, capitelle e fusti; nessun sa a che cosa esse abbinao servito ne donde siano stato portate la. This is still the case: Burckhardt noted vast quantities of shafts of columns at Om Keis and, to its north east, over 190 standing full-height, and over 100 part-shafts standing at Gerash, whilst Buckingham counted nearly 200 in reuse in the town of Acre.
5. The phenomenon draws attention to one of the most abundant sources for later centuries of examples, not only of antique architecture and sculpture, but especially of inscriptions. In this respect, military architecture may be seen not just as a reflection of social attitudes, but as an actual instrument which, by re-using the past and displaying it, keeps at least some of the monuments of Antiquity in view rather than buried, and therefore actively helps in the various revivals of interest in the classical past that, in the West, inform the Middle Ages and determine the nature and extent of the Renaissance itself . The walls, in this sense, make the city. They should not only dissuade any attacker, just as the strength of a castle does, but their architectural decoration is also intended to indicate power and wealth. In exactly the same way the Middle Ages made the Renaissance in the West, while further East spolia walls have released their treasures only much later, over the last two centuries.
But we are hampered in our assessment of mediaeval walls because of a sparsity of information about the decoration on the antique enceintes on which they were probably modelled. Our knowledge of the gates of Rome and of Constantinople is an exception here, because they were so famous. To illustrate the problem from the West: the walls of Narbonne were highly decorated with spolia antiquities, clearly deliberately. It seems more than possible that this is in imitation of antique examples, most of which have of course disappeared. For example, nearby Toulouse had a South Gate, the Porte du Chateau Narbonnais, destroyed in the 16th century, which had bas-reliefs of “captives” to either side of a trophy, framed by cannellated columns. This was almost certainly antique in origin, with the statues and the blocks probably in reuse as spolia. Thus we learn that the chateau was formed de grosses pierres de taille avant plus tot apparoissance de dépouilles, reliques et vestiges d’autres bastions que d’avoir été faits à propos grandes pierres, de quoi les murailles d’iceliu étoient construites, n’[étoitent] d’aucun mortier, ne ciment assemblees, mais seulement l’une a l’autre cramponnées et de toutes parts ainsi iontes et rangées à la règle. But it is impossible now to draw any parallels with the walls of Narbonne.
Occasionally, documents in the West suggest the reuse of antiquities in fortress walls, as at Lucera - but we do not know whether spolia were reused here for their convenience or for their beauty. Thus two documents of 1303 write of a location called Antiquallia, at Lucera - (presumably a find spot for spolia?) and requests the castellan of the fortress for materials in secondary reuse, item columpnas marmoreas et lapides antiquarum ecclesiarum pro constructione. In May 1304, another document refers to columpnas omnes existentes in fortellicia dicti castri, que non sint affixe in aliquo opere. With other documents, we are not sure whether the references are to antiquities or not.
Luckily, but again only in the West, we have in mediaeval manuscript illustrations plenty of supporting evidence for the prestige in which decorated walls were held. Such manuscripts frequently give emphasis to the importance of ramparts, of triumphal gateways, and of urban splendour. To which we can add an admiring description of the gallo-roman enceinte at Angers, c.1150, that it consistit in moenibus vetustissimis, gloriam fundatorum recensens, in quadris lapidibus, which underlines the historical dimension. These can be backed up by surviving examples, albeit partial, of surviving antique gates and their mediaeval imitators: Frederick II’s gate at Capua was, according to one author, decorated with spolia; as was Castel del Monte. Some surviving antique gates were decorated: Volterra's with heads, Perugia's with shields, several with arcading and, sometimes, figurative pilasters and pillars, some no doubt in imitation of triumphal arches. Judging by the Golden Gate at Constantinople or Hadrian's Arch at Antalya, decorated gates may well have existed in Turkey, and perhaps been imitated by the Knights, whose castle at Bodrum had Mausoleum reliefs flanking at least one gate. In Athens, for example, the Krystalliotissa Gate which probably replaces an earlier one in the north flank of the post-Herulian Wall, dating to the period of Justinian, is richly decorated, from the plentiful available materials. Similarly, the “castle” of the Acropolis at Athens was in a sense decorated, since it incorporated the Propylaea, and it is not clear from early accounts by travellers whether they realised the fact, or believed them to be constructed as part of the castle itself. Reworking with spolia could indeed be confusing: the propylaea at Baalbec, for example, included the Roman flanking towers with some Arabic cladding to the propylaea, and the Temple of Bacchus became a lofty donjon.
Even the frequent and widespread vogues for diapering of various kinds, including polychrome courses, probably originated in antique fashions of at least Hellenistic date. In this regard, what connections may be established between imitation, spolia and pastiche? When spolia walls alternate different colours of stone, this could well be in imitation of the antique, but it is also a reflection of contemporary aesthetics., and is a technique which appears in mediaeval walls in Turkey. Clive Foss (whose work on Byzantine fortifications is extensive and valuable) identifies as Metabole the site where are to be found limestone spoils (perhaps 7th century, by analogy with Ankara and Sardis) carefully arranged in regular courses. They include numerous column drums and several doorstone tombs, all apparently without inscriptions. The whole effect, enhanced by the contrast between the whitish stones and the red bands of mortar between them, is highly decorative and quite unexpected. - unexpected perhaps, but by no means unique: compare Ama, in Syria, which uses similar striations, and Haruniye, which horizontally stripes the east gate in dark and lighter coloured stone blocks. Mediaeval fortresses in Turkey were frequently built on the same site as their antique forbears, very often on top of the same foundations, and often employing and making good what was found there. Imitation is therefore likely, with bossed masonry as another deliberate evocation of antique grandeur.
Certainly antique-inspired is the vogue for bossed masonry, the origin of which is clearly and plentifully to be seen in classical Greek architecture, and in many Hellenistic fortifications in Turkey (such as Assos), to be imitated in structures such as Urfa, Haruniye, Anavarza and Korykos. It is also possible that its use is primarily practical rather than simply decorative - namely, that such a profile better withstands the shocks of projectile-throwing siege engines. Nevertheless at Rumkale, the church has bossed decoration, underlining once more how the practical and the decorative can intertwine. Enlart even suggests that it was a common practice to apply bosses to new pieces of stone to match those of spolia. But the imitation of the past might also be in play at Porta Pinciana, Rome, and at the temple at Split, which seem to imitate the small lifting bosses left on some earlier work for a decorative or perhaps apotropaic intent. The display of pagan spolia in Christian contexts, for which there is evidence in Turkey, might also have been apotropaic, just as it was for Bernward of Hildesheim in Germany. Pagan columns might sometimes have needed sanitizing as well, as with the apparent reference to Solomon’s Temple in the Pilastri Acritani.
If earlier architectural members were redolent of past prestige and important in invoking it for the present, this was all the more the case with sculpture, which had itself frequently played an essential part in the political programs of antique rulers. As Hanfmann writes of sculptural programs in Asia Minor, These sermons in stone [...] did preach a definite ideology. While official acknowledgment was made to the ruling power of Rome, the main theme was a classicizing attempt to extol the past glories of the Greek mythical world, of the city’s history, and of the Greek literary education and culture [...] while enjoying the benefits of the organizing ability and the comforts of the Roman present. Cultural “hand me downs” are an important element in several aspects of mediaeval cultural life, from law and poetry to surveying, the art of war and wine-making. Fortress building and decoration are no exception, so strongly were our forbears influenced by the continuing prestige attributed not only to the antique achievement but also to its many surviving remains. To the potency of tradition, of course, is added the sheer pragmatism of military engineers, who appear to have used the best material they could find, and frequently to have distinguished (almost as if they were painting a portrait) between the “good side” of a structure - that is, one which would be readily visible to visitors - and the others, which could safely be constructed out of inferior materials.
The point of such decoration was that it was politic to impress; and we know from travellers' accounts that they certainly admired monuments made of spolia, whether or not they realised this was how they were made. Thus Niccolo da Martoni, who visited Athens in 1394, writes: qui introytus est de lapidibus marmoreis, pulchris laboribus fabricatus, sic pulcer sicut est introytus turrium civitatis Capue (an estimation which would no doubt have pleased Frederick). But it naturally gets better inside: in quo castro est[imo?] quedam sala magna in qua sunt columpnae magne XIII, Supra quas columpnas sunt trabes longi pedibus triginta, et super ipsas trabes sunt tabule marmoree: magnum et mirabile opus videtur.. Equally, Chaucer via Boccaccio might have echoes of admiration for the “Frankish Tower” on the Acropolis.
Similarly, the great spolia walls of Africa are held in high esteem by Leo Africanus, who approaches his task in an ordered but far from formulaic fashion, so that his descriptions might easily appear in tables rather than as running text. Indeed, his book generally judges cities and their prosperity by the grandeur of the walls, which he always notes, although he sometimes had to contrast the poverty of the latter with the grandeur of the former. He always notes carefully when a city is Roman in origin, as distinct from when it is African; and he does so from a standpoint of almost complete ignorance of the Greek and Roman geographers, so that we may accept his observations as eye-witness reports. A great admirer of what the Romans left, he is no apologist for his own day, which seems to him often degraded, and he frequently condemns later generations for letting fortifications fall into ruin.Thus El Hama e una Citta anticha edificata da Romani e cinta di mura fatte di pietre grosse e molto ben lavorate, e fino di d’hoggi si veggono tavole di marmo con lettere intagliate su le porte; le case e le strade di questa citta sono brutte, e gli habitatori poveri. Urbs Citta is Roman, 190 miles south of Tunis, e sono in lei molte antiche reliquie de Romani: come sono statue di marmo, tavole di marmo su le porte con latine lettere intagliate per entro, e molti muri di pietre grosse e lavorate. The town was then taken by the Goths, deserted, and came back to life only as a village. Costantine has walls which are antiche, alte e grosse, e fatte di certe pietre negre, e lavorate, whilst at Stefe they are di pietre belle e grosse fatte in forma quadre. At Bresch, near Oran, Nella citta rimangono molte vestigia de gli edifici, e fabriche de Romani, e di quelli sono fatte le mura, just as they are at Sersel and at Deusen. He has wide experience of things Roman, and can make comparisons with what he has seen in Europe. So Tebessa he recognizes as a Roman city, e cinta d’intorno d’alte, forti e grosse mura, fatte di alcune grosse pietre lavorate, le quali somigliano alle pietre, che sono nel coliseo di Roma; ne io per tutta l’Africa, ne in tutta Europa ho veduto mura di quella sorte. Ma le case di dentro sono altretanto brutte. And at Caphsa, the walls are of grossissime pietre lavorate, come sono quelle del coliseo di Roma, and the streets are lastricate di pietre negre, come sono le strade di Napoli e di Firenze.
Leo was in no doubt about the symbolic value of the Roman inscriptions he saw displayed in spolia walls. For him they were triumphalist, and no less than the proof that the Romans have destroyed African civilization and replaced it with their own. He muses on what lost African writing would have been like, finding it strange that the inscriptions on tombs or walls should be Roman, not African. Why was it lost? Because of the inevitable and traditional annihilation by every race of the monuments of their predecessors: quando I Romani, che fur loro nimici, dominarono quei luoghi, essi, come e costume de vincitori, e per maggior lor disprezzo, levassero tutti i lor titoli e le lor lettere, e vi mettessero I loro, per levar infieme con la dignita de gli Africani ogni memoria, e sola vi rimanesse quella del popolo Romano … Non e adunque da maravigliarsi che la lettera Africana si perdutta … This theme appears in the index as Romani, destruttori delle memorie Africano. 
It is clear, therefore, that the military use of spolia, both in structure and as decoration, offers a rich source for investigation; and some sites will be studied in more detail below.
 cf. SPOLIEN in Lexikon des Mittelalters VII Munich 1995, cols 2129-2131 incl bibliography;
 R. GINOUVES & R. MARTIN, Dictionnaire méthodique de l’architecture grecque et romaine, I, Matériaux, techniques de Construction, Techniques et Formes du décor, Rome 1985, pp.103ff and plates 28-9;
 cf. A. FRANTZ, The Athenian Agora, XXIV: Late Antiquity A.D.267-700, Princeton 1988, p.126.
 Cf. the reference in MARINO, L’uso dei materiali, cit., to a MS by Rotelin (which he doesn’t himself reference) on the dismantling of the walls of the Tower of David at Jerusalem in 1239;
 C. MARSHALL, Warfare in the Latin East 1192-1291, Cambridge 1992, p. 103;
 Cited in P. EGIDI, Appunti su alcune costruzioni di Siria e di Palestina, Architettura e Arti Decorative I 1921-2, 411-417: cf. p.414;
 J.L. BURCKHARDT, Travels in Syria and the Holy Land, London 1822, pp. 272, 263-4; for the importance of columns, cf. A. SEGAL, From function to monument: urban landscapes of Roman Palestine, Syria and Provincia Arabia, Oxford 1997, pp. 5-53;
 J. S. BUCKINGHAM, Travels in Palestine…, London 1821, p.74;
 For but one example of how scholars studied spolia in walls not only for their “ornaments” but especially for the content of their inscriptions, long before the CIL, see J. RABY, A seventeenth-century description of Iznik-Nicaea, Istanbuler Mitteilungen 26, 1976, pp. 149-86; M. GREENHALGH, The survival of Roman antiquities in the Middle Ages London 1989; and now L. DE LACHENAL, Spolia: uso e reimpiego del antico dal III al XIV secolo, Milan 1995;
 M. LABROUSSE, Toulouse antique des origines à l’etablissement des Wisigoths, Paris 1968, pp.281ff. The quotation is from A. NOGUIER, Histoire Tolosaine, 1556, p.23. For an illustration, cf. P. WOLFF, editor, Histoire de Toulouse, Toulouse 1974, p.26;
 P. EGIDI, Codice diplomatico dei Saraceni di Lucera, Naples 1917; - Documents 727, 729, 758;
 L. DE LACHENAL, Il gruppo equestre di Marco Aurelio e il Laterano. Ricerche per una storia della fortuna del monumento dall'eta medievale sino al 1538, in Bollettino d'Arte, 74 (75) (1990),. Pp. 16-32. J.L.A. HUILLARD-BREHOLLES, Historia diplomatica Friderici II, V, Paris 1862, p. 912: the text of 22 April 1240, entitled de lapideis imagininus usque Luceriam mittendis et portandis - refers to bas-reliefs which might have been antique;
 P. TOUZET, L’Architecture militaire du VIIe au XIIIe siècle d’après les enluminures de manuscrits, in Bulletin Trimestriel de la Société des Antiquaires de Picardie, (1977), pp. 17-35; when the buildings inside city are represented, p.18, ils sont d’ailleurs de caractère également antique, munis de frontons, de colonnades et de toits à larges tuiles, until the 10th century;
 MORTET, Recueil, II, p. 79;
 M. CAMILLE, The gothic idol: ideology and image-making in medieval art, Cambridge 1989, p.276;
 L. DE LACHENAL, Il rilievo frammentario con cavalieri reimpiegato a Castel del Monte. Alcune note sugli esordi della scultura lapidea in Apulia, in Riv. Ist. Naz. d'Archeologia e Storia dell'Arte, XIV-XV (1991-2), pp. 131-52; cf. also DE LACHENAL, Gruppo equestre, no. 61, 1-52; and 62, 1-56, where she cites and illustrates (25-6) the equestrian group, much damaged, placed above the entrance to a ground-floor room in the courtyard of Castel del Monte, which she parallels with a nude equestrian statue/relief over an entrance gate to the castle at Lagopesole (now lost. cf. M. RIGHETTI TOSTI CROCE, La scultura del castello di Lagopesole, in A. M. ROMANINI, editor, Federico II e l'arte del Duecento italiano, Galatina 1980 (Atti del III Settimana di Studi ... Rome 1978), pp. 250-1 & fig. 28);
 K. DORNISCH, Die griechische Bogentore. Zur Entstehung und Verbreitung des griechischen Keilsteingewoelbes, Frankfurt-am-Main 1992, pp.189-91, pp.191-195, and plates 28a & 28b;
 H. BUESING, Roemische Militaerarchitektur in Mainz, Mainz 1982, pp.60-63, 261: Capua, Trier, Autun, Regensburg for arcading; Porta Praetoria at Mainz with pillars with life-size figures; and cf. P. Gros, L’architecture romaine du début du IIIe siècle avant Jésus-Christ à la fin du Haut-Empire, I: les monuments publics, Paris 1996, pp.26-55 for a typological overview of walls and city gates, and pp.56-94 for honorific and triumphal arches;
 F. S. KLEINER, The study of Roman triumphal and honorary arches 50 years after Kaehler, in Journal of Roman Archaeology, 2 (1989), pp. 195-206, for review article;
 A. GABRIEL, Voyages archéologiques dans la Turquie Orientale, Paris 1940, pp. 133ff. for the likelihood that the Karphut Gate at Diyarbakir is actually antique (hence the elegant arches and columns: his fig. 101);
 A. DE THEVENOT, Relation d’un voyage fait au Levant, Paris 1665, pp.214-6: des bas reliefs fort bien taillez contre le mur qui est battu de la mer, sont plusieurs autres pièces de bas reliefs en divers lieux. Entre la quatrième et cinquième porte il y a à main droite des bas reliefs de gens qui combatent;
 FRANTZ, The Athenian Agora, cit., p. 140; the Hypapanti Gate in the west flank of the walls uses similar jambs, and is therefore also thought to be a Justinianic repair: ibid., 139;
 cf. T. TANOULIS, The Propylaea of the Acropolis since the 17th century: their decay and restoration, Jbuch DAI 102 1987, pp.413-483, with plentiful illustrations;
 H. KOHL et al., Baalbek, II, Berlin & Leipzig 1925, fig 7 p. 41. The SW tower has a building inscription of 1219. Earliest work on making a fortress reckoned to be 11thC and 12thc (p.60);
 GINOUVES & MARTIN, Dictionnaire méthodique, cit., plate 46. K. RHEIDT, Bautechnik und Bautradition in byzantinischen Pergamon, in A. HOFFMANN et al., editors, Bautechnik der Antike (Colloquium, Berlin 1990), Mainz 1991 (Diskussionen zur Archaeologischen Bauforschung 5), 187-196: he illustrates a tower with carefully laid polychrome courses at Kizilkilar;
 M.V. SCHWARZ, Mittelalterliche Dekorationsfluege: Eine Studie ueber Schauplaetze und methoden von Antikenrezeption, in Roemische Jahrbuch der Biblioteca Hertziana, 25 (1989), pp. 97-126; and N. Kenaan-Kedar, Gli architravi della chiesa del Santo Sepolcro a Gerusalemme, in REY-DELQUE, Le Crociate, 286-90;
 C. FOSS, Byzantine Malagina and the Lower Sangarius, in Anatolian Studies, 40 (1990), pp.161-183; cf. plate XXIVc and XXVa, b;
 DE THEVENOT, Relation d’un voyage, cit., p.443: the walls are basties de bonnes pierres blanches et noires figurées en diverses façons, le peu qu’il en reste monstre leur ancienne beauté. La porte du Chasteau est ornée d’inscriptions en lettres Arabes;
 H. HELLENKEMPER, Burgen der kreuzritterzeit in der Grafschaft Edessa und im Koenigreich Kleinarmenien, (Geographica Historica, Band 1), Bonn 1976, plate 23A;
 N. ELISSEEFF, Nur ad-Din: un grand prince musulman de Syrie au temps des Croisades, 3 vols, Damascus 1967, III, p. 720, reports this for Les blocs à bossage et à refends dressés au ciseau, selon les meilleurs traditions des tailleurs de pierre syriens…;
 Ibid., plates 14, 24, 46, 52B, 53B, 55B, 65B and 11A respectively;
 C. ENLART, Les monuments des Croisés dans le Royaume de Jérusalem: architecture religieuse et civile, 2 vols, Paris 1925 & 1928, I.39;
 G. LUGLI, La tecnica edilizia romana, 2 vols, Rome 1957, pp. 214-18 and plates LIII-LIV;
 J. RUSSELL, The archaeological context of magic in the Early Byzantine period, in H. MAGUIRE, editor, Byzantine Magic, in Dumbarton Oaks 1995, pp. 35-50; cf. pp.48-49; C. MANGO, Antique statuary and the Byzantine beholder, in DOP, XVII (1963), pp. 55-75, fig. 2 & pp. 63-64 for the antique relief over the south entrance to the church of S. Anne at Trebizond, and remarks on interpretatio cristiana;
 F. J. TSCHAN, Saint Bernward of Hildesheim, 2: his works of art, 2 vols Notre Dame IN 1951-2. Pp. 275: an apt means of substituting things Christian for the things pagan that some of his people still regarded with lingering reverence;
 M. VICKERS, A ‘new’ capital from St. Polyeuktos (Sarachane) in Venice, in Oxford Journal of Archaeology, VIII.2 (1989), pp. 227-230; material from the church has turned up in Barcelona, Venice, Aquileia and Vienna;
 G. A. M. HANFMANN, From Croesus to Constantine: the cities of western Asia Minor and their arts in Greek and Roman times, Ann Arbor 1975, pp. 66-7;
 Cited in J. M. PATON, Chapters on Mediaeval and Renaissance Visitors to Greek Lands, Princeton NJ 1951, p.33;
 P. LOCK, The Frankish Tower on the Acropolis, Athens: the photographs of William J. Stillam, in Annual of the British School at Athens, 82 (1987), pp. 131-133;
 O. ZHIRI, L’Afrique au miroir de l’Europe: fortunes de Jean Léon l’Africain à la renaissance, Geneva 1991, for background to the book;
 G. B. RAMUSIO, Delle Navigationi et Viaggi raccolto gia da M. GB Ramusio, 3 vols, Venice 1563, 1564 & 1565, I, p. 1ff: Delle Descrittione dell’Africa et delle cose notabili che quivi sono, per Giovan Lioni Africano;
 L. MASSIGNON, Le Maroc dans les premières années du XVIe siècle. Tableau géographique d'après Léon l'Africain, Algiers 1906, p.160;
 J. CHRISTERN, Das fruechristliche Pilgerheiligtum von Tebessa, Wiesbaden 1976. 167f. & plate 10 for spolia, which he believes were used for aesthetic and iconographic as well as for practical reasons;
 RAMUSIO, Delle Navigationi, cit., cf. vol I. fol. 8r; for parallel remarks cf. L. de MARMOL, Libro Tercero y segundo Volumen de la primera parte de la descripcion general de Affrica, Granada 1573, chap. 34, fols 44r-44v;