Sodor Castle, also known as Castle Causeway, is an old, ruined castle that stands near the causeway on the Skarloey Railway. It was first seen in the fourth season, but its name was not stated until the seventh season episode, Rheneas and the Roller Coaster. Since then, it had appeared in every season, except the eighth, until the twelfth.
- The mountain behind the castle and the pine trees next to it were removed after the fourth season. Following the castle's return in full CGI, they were re-added.
- In the ninth and eleventh seasons, the building used for the castle was the same one used for the Ruined Castle.
- In the seventh season song, The Red Balloon, James can be seen at the castle, but the line running over the causeway is narrow gauge.