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  30 January 2015 Last updated at 11:48 GMT
  But visitors to Niagara Falls in North America got a shock when they saw adventurer Will Gadd climbing UP a frozen section.
  Niagara Falls is actually a collection of three waterfalls - he made it up an icy part of Horseshoe Falls, the biggest one.
  Will said: "I've been ice climbing for 30 years now and this is the coolest thing I've ever done."
  Watch Hayley's clip to see Will in action.
summary: When you think of waterfalls, you tend to picture stuff going down...