There seems to be a phobia for just about everything these days, from argybutyrophobia (the fear of getting peanut butter stuck in your throat) to horror vacui (the fear of empty spaces). But one of the most well-known fears is triskaidekaphobia — the phobia of the number 13. While this is probably nothing more than superstition, many people avoid the thirteenth floor in buildings and hotels, with some even going as far as avoiding living or working on that floor altogether.

The number 13 has a long history of being considered unlucky. Some believe it has to do with the Last Supper, which had 13 people at it, including Judas Iscariot — who is often seen as a symbol of betrayal. Others think it has to do with Friday the 13th, which got its name because of a real event that happened on October 13, 1307, when King Philip IV of France, who was an absolute despicable tyrant, had the Knights Templar arrested and tortured because they were in debt to him.

The number 13 has such a bad reputation that even newer skyscrapers and apartment buildings often skip the 13th floor. In fact, a recent study found that over 85% of elevator panels do not have a 13th floor button. Some have labeled the floor as M or skip it entirely, while others just leave it blank on their building map.