Saint Peter Port Harbour is located in Saint Peter Port, Guernsey. It was a natural anchorage used by the Romans which has been changed into an artificial harbour that is now the island's main port for passengers. Loose cargo, liquids and gas are shipped to and from St Sampson's harbour. Castle Cornet has formed the harbour main defence for centuries. The castle was formerly a tidal island, but since 1859 a breakwater has connected it to the enlarged harbour.