A company I have worked closely with for the last 10 years or so used to have their offices where the original owner had installed a small 10mx5m) swimming pool, on the TOP floor.
As years went by, the original occupants left and new firms moved in on various levels. One firm operated a data centre, with servers for a number of major clients. All was fine, until late one night the swimming pool sprang a leak, and around 75 cu m of chlorinated water ran down, through the joints in the concrete structure into the data centre directly below the pool.
Turned out that when they rented the space, no mention was ever made of facilities above, or they would have thought twice about locating a server cluster there.
While the data centre relocated, the pool was repaired and refilled, although to the best of my knowledge, despite it being filled, heated and the filters running, it never gets used as a pool, probably as the part of the floor that was the changin rooms had been converted to open plan office space, with glass walls out towards the hallway by the lifts.