This chapter examines the urban development of Constantinople in Late Antiquity, tracing its transformation from a small Greek settlement into the capital of the Eastern Roman Empire. It focuses on three major phases of construction: Constantine’s foundation (324–37), the Theodosian expansion (379–450) and Justinian’s rebuilding efforts (527–65). The study explores key infrastructure projects, including city walls, forums, aqueducts, palaces, churches and harbours, demonstrating how these developments reshaped the city’s urban landscape. A central theme is the political and symbolic role of architecture in establishing Constantinople’s imperial identity. Constantine’s expansion laid the foundation for a monumental capital, incorporating existing Severan structures while introducing new landmarks such as the Forum of Constantine. The Theodosian period witnessed the construction of the formidable land walls and major religious buildings, further solidifying the city’s status as a Christian metropolis. Under Justinian, Constantinopolitan architecture reached its peak, with the reconstruction of Hagia Sophia serving as a defining moment in Byzantine building traditions. The chapter also addresses archaeological challenges, noting that while much of the ancient city has been lost due to war and modern urban development, ongoing excavations continue to provide valuable insights into Constantinople’s late antique transformation.

The abolition of the poll tax in Illyricum and Thrace made automatically the estate owner’s guarantee for this void and with that the census registration and the colonate. To prevent loss of labour in these war-stricken provinces the emperors introduced in 371 and 398 the rule that, although now free from subjection, former coloni had to remain on the estate and render services. This ‘free’ colonate, which must have existed before, was also introduced in Palestine in 386. The status of the ‘free’ coloni in Byzantium looks very similar to the status of the serfs, villeins, or Hörigen in medieval West-Europe, who also were tied to a plot of land. But there were differences too: unlike in some cases there, these coloni were not in any way subjected to the jurisdiction of their masters, nor required to ask permission for marriage, etc. Further, as far as we know, there is no link between the two phenomena. If we would call them nevertheless serfs, it should always be with the adjective Byzantine.

This chapter traces the gradual unwinding of the Notitia system in response to the shifting strategic needs of the east Roman empire. Anastasius began the process by deploying the praesental armies to the east, first against the Isaurians and then against the Persians, but it was Justinian who fully dismantled them. Beginning with his creation of a new military command for Armenia and continuing through the establishment of a standing field army for North Africa and Italy, Justinain cannibalized the praesental armies and dispersed the striking power of the armies of Oriens, Thrace, and Illyricum. The consequences of Justinian’s decisions were keenly felt by his successors who struggled to defend the empire against escalating threats in the Balkans and the east. By the time Herakleios came to the throne, the Romans could barely muster three field armies, those for Thrace, Armenia, and Oriens, and it was these depleted armies that Herakleios used to defeat Persia and lay the basis for the thematic armies of Byzantium.

This chapter demonstrates that all of the available evidence indicates that the Notitia system was rapidly put into place in the 440s, likely in response to the invasions of Attila the Hun on the Danubian border. Although designed to face down the threat of the Huns, the system continued to operate as the collapse of Attila’s kingdom put increasing pressure on the eastern empire, in particular in the form of Theoderic Strabo and Theoderic the Amal, two Gothic warlords who repeatedly ravaged the Balkans and assaulted Constantinople during this period. Placed in its proper context, many central features of the Notitia system become intelligible, in particular its strong Balkan focus and the function of the praesental armies, which were used as reserve forces.