Hagia Sophia has served over the centuries as one of the greatest houses of worship in both the Christian and Muslim worlds. It was built as a church in the Byzantine style in A.D. 537 when Europe was on the eve of its Dark Ages. For four centuries after that, Christians in Europe looked to Constantinople (today's Istanbul) as the leading city in Christendom and this was its centerpiece. In 1453 the conquering Ottomans converted it into a mosque and it became a museum in 1934. Hagia Sophia marks the high point of Byzantine architecture and is the pinnacle of that society's 6th century glory days. It remains one of the most important and impressive structures on our planet. For more information on the Rick Steves' Europe TV series — including episode descriptions, scripts, participating stations, travel information on destinations and more — visit www.ricksteves.com.