The Blue Mosque was commissioned by Sultan Ahmet I when he was only 19 years old. It was built near the Hagia Sophia, over the site of the ancient hippodrome and Byzantine imperial palace (whose mosaics can be seen in the nearby Mosaic Museum). Construction work began in 1609 and took seven years. One of the most notable features of the Blue Mosque is visible from far away: its six minarets. This is very unique, as most mosques have four, two, or just one minaret. According to one account, the Sultan directed his architect to make gold minarets, which was misunderstood as six minarets.