Saint Sofia Church is the second-oldest church in Sofia and the building that gave the city its name in 1329. Built in the 6th century during the reign of Byzantine Emperor Justinian, it stands on the site of several earlier churches dating back to the 4th century and is one of the most valuable examples of Early Christian architecture in southeastern Europe. The church features a unique combination of a cross-shaped basilica with a cupola, measuring 46 meters long, 20 meters wide, with a 20-meter high dome. The underground level reveals the remains of three earlier churches and ancient Roman necropolis with frescoed tombs.