Palermo is surrounded by mountains, formed of calcar, which form a cirque around the city. Some districts of the city are divided by the mountains themselves. Historically, it was relatively difficult to reach the inner part of Sicily from the city because of the mounts. The tallest peak of the range is La Pizzuta, about 1,333 m (4,373 ft.) high. However, historically, the most important mount is Monte Pellegrino, which is geographically separated from the rest of the range by a plain. The mount lies right in front of the Tyrrhenian Sea. Monte Pellegrino's cliff was described in the 19th century by Johann Wolfgang von Goethe, as "The most beautiful promontory in the world", in his essay "Italian Journey".

What geographic form is Palermo surrounded by?