Iansholm is a tower fortress built at the edge of a cliff. The landward side of the castle has small windows and parapets for defense against enemies. The only entrance is a small door at the top of a narrow stairway, making it difficult for attackers to rush the door.

Because it cannot be attacked from the sea, the back of the castle has larger windows, which help make the interior relatively bright and comfortable.

The back of the tower can be opened to show details of the interior, including the great hall, a dungeon, a library, and sleeping chambers. Iansholm is 20" x 20" (64 x 64 studs) and stands about 27" high.