The nephew of William the Conqueror began construction of the cathedral in the early 12th century. The Norman transept towers (1107-37) that flank the nave are what remains of the original Norman cathedral following a rebuilding project begun around 1360. The west front includes an ornate Gothic screen with three tiers of sculpted figures, including Alfred, Canute, William the Conqueror, and Richard II. The nave contains the longest Gothic ceiling in the world (extending 300 feet) and there are colorful bosses studding the intersections of the ribs of the vaulting. Various Kenyon students in 1981 volunteered to work on a restoration project-- washing and painting these bosses. On the left side of the nave, the minstrels' gallery represents angels playing 14th-century instruments.