Colosseum, largest and most famous ancient Roman amphitheater. The emperor Vespasian, who ruled Rome from ad 69 to 79, began construction of the city’s Colosseum and his son, the Roman emperor Titus, dedicated it in ad 80. The Colosseum was completed by Vespasian’s younger son, Domitian, who succeeded Titus as emperor in 81. The structure was originally called the Flavian Amphitheater. Modifications and restorations necessitated by fires and earthquakes were made to the Colosseum until the early 6th century. In succeeding centuries the Colosseum suffered from neglect, earthquakes, and damage done by builders. Still, slightly more than one-third of the outer arcades, comprising a number of the arches on the north side, remain standing. The inner skeleton, which supported the cavea (seating space), is also substantially intact. All marble, stucco, and metal decorations, however, are gone.