When they want to mess with tourists, the natives make it flow the other way.
Runner up (based on votes from readers ;-)
What happens when Gaia decides to wash her son's mouth out with soap.
And thanks to the reader who identified this as Swarovski Fountain–the doorway into the Swarovski Kristallwelten, or Swarovski Crystal World in Austria
Originally posted to Welcome to Arhyalon. (link)