By the time building on Angkor Wat was begun early in the 12th century, this had been elaborated to a central tower surrounded by four smaller towers. The central monument represents the mythical Mount Meru, the holy mountain at the centre of the universe, which was home to the Hindu god Vishnu. The five towers symbolise Mount Meru's five peaks. It is difficult to express in words the enormous scale of Angkor Wat, but it can be explained in part by a look at the dimensions of the complex. The temple is surrounded by a moat which makes the one around the Tower of London, built at roughly the same time, look like nothing more than a garden trench