Mont-Saint-Michel is a mixture of Romanesque and Gothic art. The Benedictine abbey, founded in 966, was built on the site of a primitive sanctuary (built in 708) dedicated to the archangel Michael. The first abbey church, Notre-Dame-Sous-Terre, was built in the 10th century. The pre-Romanesque chapel with two parallel naves is the oldest part of the Mont. It was the master builders of the Gothic period who, whilst making the most of the limited space, devised high walls, slender masses, openwork volumes, and aerial pinnacles.