Istanbul Istanbul was the name used by at least the later half of the 20th century for an Earth city which had previously been known as Constantinople , and before that , Byzantium . ( PROSE : " Shadowmind " ) Byzantium . Byzantium was , according to Benny , the oldest name of Istanbul . ( PROSE : " Shadowmind " ) Byzantium remained the name of the city around the time of Jesus Christ . The First Doctor , Barbara , Vicki and Ian visited the city in 64 AD , and found it to be a city struggling with three groups vying for power : the Jewish Pharisee s , the Roman Empire and the adherents of the fledgling Christian religion . ( PROSE : " Byzantium ! " ) Byzantium begat New Byzantium . The Seventh Doctor once told Ace that he thought New Byzantium stole the name because the two cities had a similar geography , both cities being set " on an isthmus of land , cut through by a strait linking two sea s " . ( PROSE : " Shadowmind " ) Constantinople . The name switched to Constantinople in the early part of the first millennium . Benny once told Ace that the name switch was in honour of Emperor Constantine . She went on to say that Constantinople was " the capital of the Eastern Roman Empire until the 15th century , when it was captured by the Turk s " . ( PROSE : " Shadowmind " ) In the 3rd century , an incarnation of the Doctor encountered Fenric in Constantinople , where he defeated him at chess and trapped him in a flask . ( TV : " The Curse of Fenric " ) By his fourth incarnation , the Doctor bought a hookah in Constantinople , which he would later use as part of a ruse to evade the Chancellery Guard on Gallifrey . ( TV : " The Deadly Assassin " ) In 540 , the First Doctor , Vicki and Steven Taylor visited Constantinople . However , through the machinations of the Monk to sabotage the Doctor ' s timeline , the First Doctor ' s place was taken by the Fifth Doctor . This damage would later be repaired . ( AUDIO : " The Secret History " ) In the 10th century , the Fifth Doctor and Peri Brown visited Constantinople . ( PROSE : " Methuselah " ) Piloting the Doctor ' s TARDIS , Nardole visited 12th century Constantinople and ruled for a while as Emperor , as one of " a few accident stop - offs " before successfully retrieving the Twelfth Doctor from Harmony Shoal ' s head office in 21st century New York . ( TV : " The Return of Doctor Mysterio " ) In 1914 , the Seventh Doctor and Ace visited Constantinople to locate and dispose of a malfunctioning Krivani interstellar drive . ( PROSE : " Ante Bellum " ) In 1924 , River Song and Bertie Potts were headed to a mission in Mesopotamia . Their boat docked at Constantinople . ( AUDIO : " The Boundless Sea " ) Istanbul . By 1963 , Constantinople had become Istanbul . Susan Foreman , while taking school on Earth , once forgot the time and called the city Constantinople . In consequence , her geography teacher made his entire 4G class chant , " It ' s Istanbul , not Constantinople ! " ( PROSE : " Time and Relative " ) In the 21st century , the Ninth Doctor fought Sontaran s on a rooftop in Istanbul . Sally Sparrow saved his life from one of them , and gave him her Christmas homework for instructions for when the TARDIS would " burp " and jump forward in time twenty years without the Doctor . ( PROSE : " What I Did on My Christmas Holidays by Sally Sparrow " ) Byzantium again . The city was again known as Byzantium by the time of the Earth Alliance ' s war with the Eminence . The Alliance ' s media centre was located there . ( AUDIO : " Rule of the Eminence " ) Behind the scenes . Narratives in the " Doctor Who " universe have not , as of 2011 , particularly defined when the city ' s name changed . According to the pseudo - narrative " Torchwood " website , 4th century BC Istanbul had sewer s full of Weevil s .