The 11th century Duomo has (like Amalfi's Cathedral) 12th century brass doors and below in its crypt is a museum with religious artefacts. To its right you will see the 13th century Villa Rufolo. It was Wagner's visit to its gardens in 1880 whilst composing Parsifal that led him to write "The enchanted garden of Klingsor has been found". From this single link was created in 1953 the Ravello Festival which occurs each summer and despite being popularly known as the Wagner Festival, in fact covers a wide variety of music and performance.
http://www.360amalfi.net/?area=Ravello