The structure between the Ravelin Block and the main fort is the Engine Room. This had double iron doors and was also served by the railway. There was once an entrance into the fort cut in the curtain wall behind this building, but it is now bricked up.
The Ravelin Block is now a Museum and the fort itself is open to the public during the summer. (See the Landguard Fort Web Site for details.)
Landguard Fort for Unreal - Main page