Chora Church

Another one of Istanbul’s historic Byzantine cathedrals turned-mosque-turned-museum is the Chora Church, otherwise known as the Kariye Museum. The original church was built during the 5th century and was rebuilt several times over the centuries, but most of the current structure dates back to the 11th century.
The interior of Chora Church is not as grand as Hagia Sophia, but it features the same extensive marble work. Unlike Hagia Sophia, however, the mosaics and frescoes adorning the walls and ceilings of Chora Church all depict scenes recognisable to those familiar with Christianity. The lives of Jesus Christ and the Virgin Mary are featured predominately.

Get Cultured: There are no signs, so it is easier to appreciate the beauty of what you are seeing if you understand more about it. The available audio guides are actually decent and cost 15 TL each. Or if you have a larger group, you can haggle with one of the guides.
*IMP Free*