Fallon is UNDER the hotel (pg. 163)

He sank back on the cool earth and looked up into the darkness that was the underside of the floor above (pg. 164)

He sat up again, grasping her arm. There was an old door, he remembered, that opened at the back...
He found the door... (pg. 165)

THIS MAY NOT BE AN ERROR, but why was there a door under the Hotel?
Was it that high off of the ground?