It is a unique urban architecture made by the finest architects. It is the largest clock in the world, where the calls of prayers are announced from it five times a day. This clock holds the words of Takbeer (Allah Akbar), and during the calls of prayer of the 21.000 light bulb located on top of this clock are lit up in white and green. These lights can be seen from 30 km far; even those with special needs can now learn that it is time for prayers just by looking at the clock. There are four clocks on each side of the tower, two main ones. One facing the Grand Mosque to the north, and another on the other side facing the south and they are 80m tall, 65m wide and 43m in diameter. The other two sides of the clock face the east and the west and they are 65m high, 39m wide and 25m in diameter. Makkah Royal Clock Tower is the tallest worldwide; it is 40m in length and 400m in height.