Basilica Cistern
The city's most unexpectedly romantic attraction, the Basilica Cistern, offers an insight into the complicated system that once brought drinking water into Istanbul from Thrace (an area of the south-east Balkans now constituting Turkish land n the European mainland, and a chunk of Bulgaria). Constructed in the sixth century and then forgotten for centuries, the cistern that once stored the water has been fitted with lights and music. Fish flitter around the bases of the 336 columns that support the ceiling. Don't miss the upside-down head of Medusa that forms the bottom of one column, proof that Byzantine builders saw Roman relics as little more than reusable rubble.