Built by the Karakhanid ruler Arslan Khan in 1127. According to the legend Arslan Khan killed an imam. The imam asked the khan in a dream to lay the imam's head on a spot where nobody can tread on it. Thus the tower was built over the imam's grave. With a height of 47 m it is Bukhara's landmark. In its ornamental bands the glazed blue tiles were used for the first time in Central Asia. It gets its nickname as the "Tower of Death" because they once executed criminals by taking them to the top and pushing them out, leaving them to fall to their death. This practice stopped in the early 1900s.