3. Abraj Al-Bait, Saudi Arabia (601m, 1,972ft)
While a lot of mega-structures can be cast purely as vanity projects, despite being the most expensive building ever built at $15 billion, the Abraj Al-Bait tower in Mecca has an undeniably practical side (and it’s not just telling the time).
Built as part of the King Abdulaziz Endowment Project, with the explicit intention of modernizing the ancient pilgrimage centre, which caters for literally millions of visitors every year, the Abraj Al-Bait is a necessarily vast hotel, located just metres away from the Great Mosque of Mecca, Islam’s most sacred site.
Opening its doors in 2011, the building’s most distinguishing features are of course the four vast clock faces adorning its highest point – they are also the largest clock faces in the world: each measures 46 metres across and is illuminated by 2 million LEDs, making prayer time hard to forget!