Thanks, I had some time on my hands :-D

On that photo, the way you're talking about is just out of sight around the building, to the left. So you may be confusing it with the shelter over the main entrance on the north side (which admittedly I didn't map). I've made another edit which adds the entrance structure, in case that clarifies. The bit on the other side (from my own knowledge of it) has a basement space, while the ground floor is just a flat terrace.