The picture above is that of the Prophet's Mosque in Madinah, Saudi Arabia, shown here with hundreds of thousands of worshippers gathered for prayer at sunset - in, around and on the mosque. Accommodating more than 1 million worshippers, the mosque is almost 1.5km long and 1km wide. The floor is made of marble, both inside and around the mosque. Each 105m tall minaret is topped with a 4 ton gold-plated crescent. The Prophet's Mosque is the second holiest place in the world to Muslims, in which Prophet Muhammad's (PBUH) grave still lies today. The mosque was originally built by Prophet Muhammad (PBUH) in 622 CE, then consisting of only an 805 square metre (about the size of 2 basketball courts) open courtyard, surrounded by a wall made from bricks and tree trunks.