Castle Cornet

Castle Cornet stands on a tidal rock at the mouth of St. Peter Port harbour, connected to the shore by a causeway that is covered by the sea at high tide, restoring the castle's island isolation for a few hours each day. The castle was begun in the 13th century and substantially rebuilt in the 17th century after being slighted during the English Civil War, so the present structure is a product of medieval origins and later military engineering rather than a single period of construction.

The interior is organised around two main courtyards with ranges of buildings including a great hall, governor's quarters and a series of gun batteries at various levels. The medieval great hall is one of the most interesting surviving spaces, with thick granite walls and narrow windows overlooking the harbour mouth. The castle's museum houses artefacts from the 16th to 19th centuries, including military uniforms, cannon and model ships.

From the upper batteries the view across the harbour is exceptionally clear: St. Peter Port town rises up the hillside behind the inner harbour, and on a fine day Herm Island and the Normandy coast are visible beyond. The military engineer who designed the batteries understood the commanding position of the rock, and the arrangement of guns here made the harbour extremely difficult to attack from the sea.

The castle was used as the official residence of the Governor of Guernsey until 1890, when the military function of the island was reorganised. After that it became a barracks and was later adapted for use as a summer residence. The castle was opened to the public in the 20th century and is now managed as a heritage site by the States of Guernsey.

The castle's relationship with the harbour changes throughout the day as the tide rises and falls. At low water the causeway is fully exposed and visitors can walk across; at high water the castle appears to float above the harbour in a way that makes its strategic position easy to understand. Evening events are held in the castle during summer, when the floodlit stone takes on a different character from the daytime visit.

The castle's museum contains a remarkable collection of items relating to Guernsey's maritime history, including ship models, navigational instruments and items recovered from shipwrecks in the harbour approaches. These objects give a material context to the harbour's long history as a port of call for vessels navigating the Channel, and they ground the castle's military history in the commercial life of the sea.

It is Guernsey's principal historic monument and one of the best-preserved island castles in the Channel Islands.

The tidal isolation of the castle at high water is a unique feature that reinforces its original defensive purpose.

The panoramic views from the upper batteries across St. Peter Port harbour are among the finest in the islands.