Castle Cornet is a historic castle located on a small island in the harbor of St. Peter Port, Guernsey, in the Channel Islands. The castle has a rich history that dates back over 800 years and has served as a fortress, a royal residence, and a military barracks. The castle is surrounded by a series of walls, bastions, and gates that were built over several centuries to defend the island from invaders.

The castle was first built in the 13th century and has been expanded and modified over the years. During the Hundred Years' War, the castle was captured by the French and held for several years before being recaptured by the English. It was also used as a garrison during the English Civil War and the Napoleonic Wars.

Today, Castle Cornet is open to the public and houses several museums and exhibits that showcase its history and heritage. Visitors can explore the castle's many rooms and chambers, including the Governor's Apartments, the medieval kitchen, and the dungeons. The castle also features several gardens, including a herb garden and a rose garden.