Begin your day in the subterranean depths of the Basilica Cistern, a 1,500-year-old building supported by 336 columns. Don’t miss the twin blocks carved into snake-haired Medusas.
Right across from the cistern is the greatest single building in a city full of wonders, the Hagia Sophia or Aya Sofya (£8.70, closed Mondays). It was a church, then a mosque and is now a museum.
