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6 September 2014 Last updated at 16:11 BST
The Slide on Cancer in Londonderry's Shipquay Street was organised by Cancer Research UK as a fundraiser.
The custom-built slide is open from 10.00-17:00 BST on Saturday and Sunday.
Participants launch themselves onto the slide at the top of the street and finish at Shipquay Gate in a huge "splash zone."
A slide running the entire length of one of the steepest city centre streets in Europe has been turned into a massive three-lane water adventure.