The Blue Mosque is one of the great religious buildings in the world. Built by the Sultan Amhet in 1609-1616, it is a marvel of proportion, harmony and beauty and one of the highest achievements of Ottoman architecture. It is called the blue mosque because of the blue Iznik tiles that line the interior. When entering the mosque you feel a sense of timelessness. The architects modeled it somewhat on the Haghia Sofia which stands across the street. In a testament to the brilliance of the 6th century Greeks, the dome of the Blue Mosque uses four massive pillars which are unnecessary in the Haghia Sofia even though it was built 1000 years before! Ride at the Ramadan festival. It is still today one of the cities most active mosques.