Hagia Sophia is a former Orthodox basilica that later became a mosque, and is now a museum in Istanbul, Turkey. From the inside, I would have said it was a mosque, but the current Turkish government has strictly prohibited the building from being used as a place of worship.
I visited the building today, paid my 25 Turkish Lira to get inside and then spent a little over and hour walking around and taking pictures. Because the place is marketed as a museum I thought there would be more to the place. Instead, I found just one massive building constructed out of columns, domes and a few impressive mosaics. There were also a number of small gift shops scattered throughout the structure.
Travel tip: No, you don’t have to wear long pants to get into Hagia Sophia. And yes, you can take photos inside the building.