I don't know when there was such a mental hospital in the world.
It has appeared on the busiest streets of Gotham City, and has also been hidden in the darkest corners of Raccoon City. It may have had a short description in "The Sherlock Holmes", or it may have had a second in the film "Hannibal"...
Some people said that the girl in the nurse's uniform looked a bit like Harley Quinn. Others said that the old man in the ward on the second floor called himself Professor Moriarty. Some people found an old electric saw in the corner of the corridor, and some people dug out playing cards with a clown under the bed. The attending doctor always looked lazy, and inexplicable blood stains always oozed from the cracks in the floor.
If one day you happen to see a strange hospital on your way to get off work, then whether you are sick or not... Welcome to visit.