The Bell Tower
The Bell Tower marked the old geographical center of Xi'an, when it was known as Chang'an, and was the ancient capital of China. It was originally built to tower over the landscape as a sign of the city's power.
When the city of Xi'an grew, and the geographical center changed, the tower was moved piece-by-piece over 1,000 feet to the city's new geographical center. While it used to be across from the Drum Tower, this is no longer the case, but the two buildings remain "sister buildings."