Istanbul

Byzantium was an early Earth city that later came to be known as Constantinople and Istanbul. It became part of the Roman Empire.

Torchwood believed that the sewers of fourth century Byzantium had a Weevil population. (torchwood.org.uk)

The doctor visited the city in his first incarnation in 64 AD.

By the 27th century a city of New Byzantium existed on the human colony world of Tairngire, and at some point in the future, probably the 61st century, a New Byzantine Calendar was in use. (DW: The Doctor's Daughter). A spaceship called the Byzantium was also commissioned at some point. (DW: Silence in the Library)