This 10th century double-naved Byzantine church (now the Fenari Isa Mosque) has one of the most unusual layouts in Istanbul and is a surprising haven of beautiful Byzantine atchitecture and decoration. It is larger than it appears at first. Well worth a visit.

Access: On Adnan Mendered Bvd (one of the city's main thoroughfares) and open during mosque open hours.

As with all Istanbul's open-air cisterns it is very difficult in a photograph to show the scale of the construction. They will only really interest the die-hard Roman fan. This 5th century water tank is so large there is a park built within it. The walls of the cistern are visible across from the edge.

Access: Open at all times

Very hard to find and barely visible even then, this will interest only the die hard fan. This is the huge monumental base for Arcadius' great column. It is a massive stone pedestal jammed between two houses and half obscured by a tree. It is completely undecorated, worn and shapeless.

Access: Freely visible at all times on Haseki Kadin Sokak, up the road from the Cerrah Pasa Cami.