Did you know there was a glass wall there? I certainly can't tell from the map. Where was it?
The map shows a narrow isthmus-like segment connecting the main building to the "island" building in the pond. It was like a glassed-in breezeway. It's clearly mapped as a building / wall, but from a distance you might think you could get through there, since it's glass and looks like a great route to #2. ;-)