The Hassan Tower is a minaret located in the city of Rabat, Morocco. It is a part of an incomplete mosque complex which was intended to be the largest mosque in the world. The construction of the mosque was begun in 1195 by the Almohad Caliph Yaqub al-Mansur, but it was never completed and the tower is the only part that was left unfinished. The tower stands at 44 meters (144 ft) tall, and it is considered a masterpiece of Almohad architecture, characterized by its red and white stone stripes and its horseshoe arches. The tower is a UNESCO World Heritage Site and it is open to visitors all year round. Visitors can climb to the top of the tower and enjoy panoramic views of the city of Rabat and the Bouregreg River.