Here is the inside of Hagia Sofya. This building was once the largest church in the Christian world: built in the 6th century. It was later converted to a mosque, which meant that all its mosaics were covered with plaster, as it is forbidden to have any images in a mosque. Now Hagia Sofya is a museum and when it was being restored the curators discovered many of the mosaics were perfectly perserved because of the plaster's protection!