The Mecca Clock Royal Tower, a 577-metre tower overlooking the holy city. The Mecca Clock Royal Tower is also going to house an 858-room hotel. The complex, which will overlook the Grand Mosque that Muslims face for daily prayers. The Makkah Clock tower will be the biggest clock tower in the world as well as being the second tallest building. This article also has some great picture and videos of the whole development and the view of the Haram from the top of the biggest clock tower in the world. The tower is made up of 662 metres of concrete structure and a 155-metre crescent-topped metal spire.