Castle Cornet

Castle Cornet is a medieval coastal fortress on a small island guarding St Peter Port harbour in Guernsey. It dates back to the medieval period and was expanded in later centuries to adapt to changing military technology.

On site are a medieval keep and extensive ramparts and batteries, which illustrate the long history of harbour defence at St Peter Port; many parts of the castle are accessible to visitors and contain displays about the island’s military past. The grounds include gardens and promenades around the fortifications.

The castle has been a prominent landmark for the town across centuries, functioning historically as a defensive fortress and administrative residence.

Castle Cornet sits immediately offshore from St Peter Port and is visible from the town waterfront; seasonal visitor access is provided from the harbour area.

• Harbour position: The castle occupies an island position at the entrance to St Peter Port harbour and is approached from the town by a short causeway; it has served both defensive and administrative roles through its history.

What to See #

• The Keep: A central medieval keep and surrounding curtain walls dating from the original medieval construction phases that dominate the site's silhouette.
• Ramparts and batteries: Seaward ramparts and gun batteries reflecting later artillery-era modifications that were added to strengthen the harbour defences.