Ulfstead Castle is the home of the Duke of Sodor. It is on loan to the Island Record Office at Suddery and the Duke lives on the outskirts of Ulfstead.
In the television series, the castle was owned by King Godred in the olden days. Now, the castle is part of the estate owned by Sir Robert Norramby. It has rails running through it, much of them dual-gauge, and its own station. There is a mine beneath the castle and it also has its own crane. Millie works here and does a variety of jobs including helping the groundskeeper and taking tourists around the estate in an open-topped carriage. Stephen also works here as a tour guide.
The castle has its own park area which is home to several deer including one that Luke once befriended. The park area is tended to by a groundskeeper who has his own lodge on the castle's grounds.
In Thomas the Slender Engine
At Dawn, it is inhabited by Glynn.
At Day, it is inhabited by Caitlin.
At Night, it is inhabited by Stephen.