i believe there is a stairway - you can see a small protrusion from the platform in your reference pic - the stairway goes in both directions - one of them is for the entrance and the other for the exit - the stairways meet near the center of the building directly in front of the main doorway - they are hidden behind the protrusion. i know that's kind of confusing but it's as clear as i can make it without drawing a picture