They include six double encircled towers and a bastion tower. The city is located on a rocky hill below the abbey and has grown around the only road Grande Rue street that leads to the sanctuary.
In the northern part of the island is the Gothic monastery of La Merveille, built between 1211 and 1228. It houses, among other things, a scriptorium where the monks copied manuscripts, and in 1469 the hall became the meeting place for the members of the Order of the Knights of St. Michael.
