Why Are Some Muslims Calling to Replace GMT with Mecca Time? | Culture | Religion Dispatches. This summer, the world’s largest clock began its first official duty: marking time during Ramadan in Mecca—Islam’s holiest city. This colossal clock bears a striking resemblance to Big Ben, and the tower that hosts it (courtesy of the Canadian-based Fairmont hotel operation) is six times taller than the British landmark, making it the second tallest building in the world, visible for 16 miles. All well and good. One can marvel at human ingenuity and move on. However, what makes this case interesting is the…