The great five-aisled basilica of the city's patron — over the saint's tomb.
Hagia Sophia, an 8th-c. domed basilica — a UNESCO monument.
The Acheiropoietos, a 5th-c. early-Christian basilica.
St Panteleimon — an elegant Palaiologan cross-in-square.
Church of the Transfiguration — a small domed church.
The Byzantine walls that defined the city for centuries.