It looks like a main menu screenshot to me with an old Aperture test as the background.
Comment History
saxlover98 - - 2 comments @ A Unique Screenshot
Good karma+2 votes
saxlover98 - - 2 comments @ Alive & Kicking
Good karma-2 votes
It appears you crash down into a almost identical testing track in Portal 2. If you notice, the tests aren't the same as in Portal 1 in that track. So, it would make sense the ceiling isn't glass.
Profile
saxlover98
Kelby joined
No information given.