Page "Justinian I" Paragraph 64

Justinian also strengthened the borders of the Empire from Africa to the East through the construction of fortifications, and ensured Constantinople of its water supply through construction of underground cisterns ( see Basilica Cistern ).

To prevent floods from damaging the strategically important border town Dara, an advanced arch dam was built.

During his reign the large Sangarius Bridge was built in Bithynia, securing a major military supply route to the east.

Furthermore, Justinian restored cities damaged by earthquake or war and built a new city near his place of birth called Justiniana Prima, which was intended to replace Thessalonica as the political and religious center of the Illyricum.