Istanbul is a major city in Turkey, which is located in Europe and Asia along the Bosphorus Strait. The Old City reflects the cultural influences of the various empires that ruled the region. In the Sultanahmet district, the open-air Roman-era Hippodrome was a chariot-racing venue for centuries, and Egyptian obelisks also remain on the site. The iconic Byzantine Hagia Sophia has a soaring 6th-century dome and rare Christian mosaics.