"Istanbul or Lisbon"

Hagia Sophia
Public DomainHagia Sophia
The narrator offers these as two cities to which a hypothetical beautiful woman desired by Tomas might have disappeared by train (although this is offered as a metaphor to describe Tomas's feeling when he realizes how he misses the tall, stooped editor who disappeared before Tomas could have gotten to know him better).

Istanbul is a megacity in Turkey -- the fifth largest in the world -- and it stands on both sides of the Bosphorus Strait that runs between the Aegean Sea and the Black Sea and constitutes the border between Europe and Asia. During the eras of the Byzantine and Ottoman empires, Istanbul was known as Byzantium and then Constantinople. Lisbon is the capital and largest city of Portugal.

The two cities are situated roughly at the far southwestern (Lisbon) and southeastern (Istanbul) edges of the European continent. Hagia Sophia, the former Greek Orthodox basilica, then a mosque, is now a museum in Istanbul.