Medieval Fortifications in the Balkans

By Alice Isabella Sullivan

Fortified locals are prominent features of the Eastern European landscape. Throughout the Middle Ages, the regions of the Balkan Peninsula were caught at the crossroads of competing worldviews and defensive architecture became an important mechanism through which to ensure the protection of secular and religious sites.

Medieval cities regularly received surrounding enclosures. Constantinople is a prime example. Its massive fortifications resisted besiegers for more than a thousand years. Thessaloniki – a prominent city in the Balkans, established by King Cassander of Macedon (r. 305-297 B.C.) – featured imposing fortifications like those of the Byzantine capital. Although the architectural record of Thessaloniki from this period is difficult to establish, the walls of the city were impressive. They extended for about 8 kilometres, and were reconstructed between 380s and mid-400s. This project corresponds roughly with the rebuilding of the land walls of Constantinople under Emperor Theodosius II (r. 402-450), which began in 412-413. The Theodosian walls, with remnants still standing, consisted of a double enclosure system: an inner, main wall and an outer wall, both with towers, separated by a space in between, and preceded by a moat. The archaeological evidence and extant inscriptions reveal that the walls of the city were rebuilt once more before and after the Arab attack of 904.

City wall in Thessaloniki, Greece – photo by Julian Nyča / Wikimedia Commons

Like Thessaloniki, other fortified locales started appearing throughout regions of the Balkans during the 5th century, as evident in residential, ecclesiastical, and monastic buildings and complexes. Emperor Justinian I (r. 527-565), for example, was very active in the fortification of the Balkans. According to his court historian, Procopius, Justinian restored the fortifications at close to 250 sites and built anew over 140 fortifications.

Other large cities, such as Caričin Grad in south-east Serbia, built anew in the 6th century, also received a fortified enclosure. The city consisted of an acropolis (at the peak of the hill), upper town, and lower town, with a sewer system below, all enclosed within a massive wall with monumental gates. The city also had a palace complex, a three-aisled basilican cathedral with an adjacent baptistery, and nine other churches – all constructed out of brick and local stone. In its main features, as scholars have noted, the city offered an abridged version of the imperial capital of the Byzantine Empire, Constantinople itself. When the city of Pliska was designated as the capital of the First Bulgarian Empire in the 9th century, it too received fortifications and, later, churches, akin to the prominent capital cities that preceded it.

Aerial view of the fortified complex at Caričin Grad, Serbia, 1937 – Wikimedia Commons

The ecclesiastical fortifications often emulated those encountered in the secular context, which generally followed Roman examples. From the beginning, monastic communities set up enclosures in efforts to delineate the monastic sphere and set it apart from the rest of the world, as well as to protect it in times of need. Although the archaeological remains cannot reveal extensive details about the fortifications of earlier monastic sites, it is known that from the 11th century onward the surrounding structures took on large proportions. The Monastery at Daphni, near Athens, well known for its 11th-century church, received rectilinear fortifications surrounding the entire monastic complex (measuring about 93 x 100 metres). Scholarly opinions still oscillate on the dating of these fortifications between the 5th century and the Middle Byzantine period (9th-13th centuries).


By the 14th century, the monastic complexes routinely received fortifications in efforts to restrict access to the monastic community, as well as anticipate and withstand confrontations. A prime example is Studenica Monastery in Serbia, built by Prince Stefan Nemanja (r. 1166-1196) in 1190. The practice of fortifying monastic complexes was common throughout the Eastern Christian cultural sphere. The famous Monastery of St. Catherine at Mount Sinai, the 6th-century Justinianic church, was fortified in the manner of a Roman camp, as were the monasteries on Mount Athos – the peninsula in Greece that is home to a pan-Orthodox community of Christians.

In addition to monasteries, which regularly received enclosures, other ecclesiastical complexes did as well. The 5th-century religious site known now as the Stag’s Basilica at Pirdop, in Bulgaria, preserves a fortress built in relation to the church. Although the evidence remains elusive, it is possible that this was an episcopal church. Fortified Christian monuments across the Balkans thus combined religious and military functions, offering spiritual and physical protection for their varied communities.

In addition to cities, monasteries, and ecclesiastical compounds, the archaeological record reveals other types of fortifications in regions of Eastern Europe. These include domestic architecture and large castella, among others. These are usually more rectilinear complexes, positioned on a hilltop and with a lower enclosure, usually more irregular in shape. The hillfort at Balajnac near Niš likely had a sizable population; remains of a three-aisled basilica and a large underground cistern have been uncovered at the site. Oppida and oppidula, or “miniscule cities,” were also enclosed. They were often positioned on high, dominant locations and displayed irregular layouts dependent on the topography of the land. Important early examples are preserved at Čučer, near Skopje, and Qafa, south of Elbasan in Albania.

Ruins of the villa complex at Polače, island of Mljet, Croatia – photo by strudelt / Flickr

Finally, smaller-scale fortifications include tetrapyrgia, which were simple, miniature forts consisting of a square enclosure with corner towers. Remains of such fortifications have been uncovered at the monastery of Hagia Matrona near Thessaloniki, at Malathrea in southern Albania, and on the Monemvasia peninsula in southern Greece. Residences were also enclosed, especially if they belonged to an important individual or family. The 5th-century villa complex at Polače, on the island of Mljet in Croatia, displayed on the main façade facing the harbor two large cylindrical towers (13 metres in diameter). Flanking the façade, these towers gave the impression of a massive, fortified locale, deploying thus military forms in domestic architecture for symbolic purposes.

Fortified locales are found across the Balkan Peninsula, and the archaeological data reveals that fortification projects only gained momentum from the 6th century onward. The turmoil brought on by conflicts, on the one hand, contributed to economic, political, cultural, and demographic shifts. On the other hand, it resulted in innovations in military architecture. The Avars, Persians, and the Slavs posed a great threat to Byzantium and the Balkans for the first half of the 7th century. For instance, the Avar-Persian attacks attempted to put Constantinople under siege in 626, and the Arab-Byzantine wars between the 7th and 11th centuries were equally ineffective. Some of the attacks in the Balkans, however, were successful and gradually transformed the architectural landscape of the region.

Alice Isabella Sullivan is an art historian specializing in the medieval history, art, and culture of Eastern Europe and the Byzantine-Slavic cultural spheres. She has authored award-winning publications, is co-editor of Byzantium in Eastern European Visual Culture in the Late Middle Ages, and co-founder of North of Byzantium. Follow her on Twitter @AliceISullivan


Click here to read more from Alice Isabella Sullivan

Further Reading:

S. Ćurčić, Architecture in the Balkans from Diocletian to Süleyman the Magnificent (Yale University Press, 2010).

N. Duval and Vladislav Popović, eds., Caričin Grad. III. L’acropole et ses monuments (cathédrale, baptistère et bâtiments annexes) (Ecole Française de Rome/Institut Archéologique, 2010).

V. J. Gazić, “Urban Development from Late Antiquity to the Middle Ages: Dubrovnik, Split, Trogir, Zadar – The State of Research,” Archaeologia Adriatica 5 (2011): 151-196.

G. G. Gounaris, The Walls of Thessaloniki (Institute for Balkan Studies, 1982).

I. Mikulčić, Spätantike und frühbyzantinische Befestigungen in Nordmakedonien: Städte, Vici, Refugien, Kastelle (C. H. Beck, 2002).


R. Ousterhout, Eastern Medieval Architecture: The Building Traditions of Byzantium and Neighboring Lands (Oxford University Press, 2019).

Top Image: Bada Vida Fortress, 10th century, Vidin, Bulgaria – photo by Klearchos Kapoutsis / Wikimedia Commons


Sign up for our weekly email newsletter!