They say travel broadens the mind, but it appears that some vacation destinations can actually blow your mind.
The cities of Florence, Jerusalem and Paris all have psychiatric disorders associated with them - and tourists are the most likely to fall prey to them.
Paris Syndrome is an affliction primarily affecting Japanese tourists visiting the City of Light for the first time, who succumb to extreme culture shock and the shattering of their romantic image of the city.
While an encounter with a rude Parisian waiter may be considered par for the course by most Western tourists, BBC News reports that for the Japanese - used to a more polite society in which voices are rarely raised in anger - the experience of having their dream city turn into a nightmare can simply be too much.
Wikipedia describes the symptoms of Paris Syndrome as including "acute delusional states, hallucinations, feelings of persecution, derealization, depersonalization, anxiety, and also psychosomatic manifestations such as dizziness, tachycardia and sweating."
According to The Atlantic Monthly, at least 20 tourists, most of them Japanese, were affected by the disorder in 2011.
According to BBC News, the Japanese embassy in France operates at 24-hour hotline for those suffering from extreme culture shock, which will help sufferers find counseling or other appropriate assistance.
Jerusalem is a city of huge importance for three of the world's major religions - Christianity, Judaism and Islam - and pilgrims to the city often become overcome with emotion when visiting significant religious sites.
Some tourists however, become so consumed with religious fervor that they come to believe that they are figures from ancient religious stories, including King David, Samson and indeed, Jesus himself.
How Stuff Works describes a case study of a Jerusalem Syndrome sufferer:
A middle-aged American decided that he himself was actually Samson. The modern-day strongman got an idea that part of the Western Wall needed to be moved. He spent time bodybuilding and came to Israel to move it. After a skirmish with authorities, he landed in a psychiatric hospital.
While at the hospital, one of the mental health professionals inadvisedly told the man that he was not, in fact, Samson. "Samson" smashed through a window and escaped the hospital. A nurse found him at a bus stop and praised his Samson-like strength, at which point he cooperated.
Wired describes the experience of another Jerusalem Syndrom suffer who heard a voice commanding him to fast for 40 days and 40 nights.
The Jerusalem Syndrome was first identified in 1982, by Israel's Dr. Yael Bar-El. In the video below, which was shot in 1994, the doctor says that the city's psychiatric hospitals had treated over 500 in-patient cases of Jerusalem Syndrome in the preceding 12 years, and many more as out-patients.
Also in the video below, tour guide Ido Keyan describes how Jerusalem syndrome sufferers "forget about English - they don't know English anymore. They speak in tongues."
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Florence Syndrome, also known as Stendhal Syndrome is, a psychosomatic disorder that causes rapid heartbeat, dizziness, fainting, confusion and even hallucinations when an individual is exposed to art, usually when the art is particularly beautiful or a large amount of art is in a single place.
Though not exclusive to the city of Florence - the syndrome takes its name from 19th-century French author Stendhal, who wrote of feeling overcome by the beauty of the Renaissance artworks he encountered in Florence during his travels in Italy in 1817.
The Palazzo Medici Riccardi in Florence, the interior of which is almost entirely covered with incredible examples of Renaissance art has, according to the Daily Telegraph, caused visitors to "swoon, in particular, in the palace's chapel, which features a vivid 'Journey of the Magi' – a portrait of Medici family members from the 15th century."
Symptoms of Florence Syndrome include vertigo, fainting, confusion and even hallucinations.