The beer bottles have been removed! The window was open yesterday and I could smell beer as I walked by despite the cleaning.
Apparently, the building is a fraternity.
Obviously, you say.
The windows just past the recently un-entombed party room reveal a loft bed with a disco ball suspended underneath. And, as the strongest proof yet, this morning when I walked by on my errand to assuage my croissant addiction, I had to step around a portable urinal.
They can be rented for parties in the Netherlands. Disco ball not included.
(This photo is from wikipedia commons. I had not the presence of mind to take my camera on the croissant run and the urinal was removed by the time I left my apartment again.)