There are good cleaning ladies and there are bad cleaning ladies. Bad cleaning ladies? You want to avoid. Good cleaning ladies? They sometimes do bad things by being too good. Like the cleaning lady who cleaned a "dirty" art piece on accident.
The sculpture in question, When It Starts Dripping From The Ceiling, was made by German artist Martin Kippenberger. It's a tower of wooden slats with a trough at the base of the sculpture. Inside that trough, Kippenberger (who passed away in 1997) had spread a layer of paint to mimic a dried rain puddle. People loved it. People loved Kippenberger. People valued the piece to be worth $1.1 million (around £686,000).
Not anymore though. When the cleaning lady saw that the trough with the faux rain puddle, she did like any good cleaning lady would—she cleaned it. She scrubbed the patina off the walls of the trough to the point where it's sparkling new, accidentally stripping away the 'art' of it. Whoops! The Ostwall Museum in Berlin, Germany isn't sure what to do with the piece yet but it remains on display for the time being [Guardian UK]