The legendary portable swamp created by Fred and George Weasley was once large enough to consume the entire middle section of the first floor corridor, leading from the Dark Arts office to the History of Magic classroom. Nowadays, only a small section of the corridor is roped off in tribute of the redhead twins' swamp, but it is a historic section nonetheless.

The remaining swamp still SMELLS like authentic swamp, LOOKS like authentic swamp, BUBBLES like authentic swamp, and will suck you in like an authentic swamp, if you so wish to step in it. Avoid the swamp with care is the best advice you should heed while on the first floor, especially if you're running late to class.