Hassan Tower in Rebat, Morocco

Hassan Tower is the minaret of an incomplete mosque. It was commissioned near the end of the 12th century. The tower was intended to be the largest minaret in the world, and the mosque, if completed, would have been the largest in the western Muslim world. Construction on the mosque stopped in 1199. The minaret was left standing at a height of 144 feet. The rest of the mosque was left incomplete, with only the beginnings of several walls and 348 columns being constructed.