According to Islamic tradition, only God can create images of holy beings, including angels and prophets. Therefore, when the Ottomans converted Chora Church into a mosque in the 16th century, they covered the 14th-century Byzantine mosaics and frescoes depicting the life of Christ and Mother Mary. Hidden behind wooden shutters were some of the finest mosaics in the world, which were restored following World War II and can now be viewed in all their glory.
If you enjoy the sparkly mosaics in Hagia Sophia but didn't enjoy jostling for elbow room to look in detail, a trip to Chora Church is in order. Its Byzantine mosaics and frescoes were preserved when the original church was converted into a mosque, then uncovered and restored when it was made into a museum in the mid twentieth century. To reach the museum, it's best to find a bus or taxi from Eminönü as it's located outside the old city walls. Keep your neck stretched and limber, you'll spend a lot of your visit looking up.