Suddery Castle is a ruined castle located near the town of Suddery, overlooking the Harbour.
It is a Norman type castle with a keep, built at the end of the 12th century to fill a gap in the city's defences after a Manx raiding party failed to loot the city but instead stole a number of ships.
It was blown up during the Great Rebellion by parliamentary troops, but was refortified during the Napoleonic Wars. The demolished masonry slid down into the ocean, blocking the access for most boats into the Harbour. Because of this the Harbour has since been turned into a marina, which has become well-known for yacht traffic and regattas.
In the television series the castle ruins appeared in the second and seventh seasons, with a different appearance in each.
- Season 2 - Saved from Scrap, Thomas and Trevor (deleted scene), Percy and the Signal, Percy and Harold, A Close Shave, Break Van, The Deputation, Woolly Bear and Thomas and the Missing Christmas Tree
- Season 7 - Emily's New Coaches, James and the Queen of Sodor, Bad Day at Castle Loch, Peace and Quiet, Harold and the Flying Horse, Best Dressed Engine, Gordon and Spencer (deleted scene) and Not So Hasty Puddings