Luxor Temple
The active Abu Haggag Mosque () is located within the temple, standing on the ancient columns themselves. That part of the Luxor Temple was converted to a church by the Romans in 395 AD, and then to a mosque in 640, which is more than 3,400 years of continuous religious worship. Hence, the Luxor Temple is the oldest building in the world at least partially active for other than archeological or tourist purposes.