The biggest "slide" in the world:
Dam spillways are used to release water in case of a flood, but sometimes these spillways are also used as a slide for kayakers and even bikes. This is the case with Europe's largest dam spillway which is part of the LIyn Brianne dam in Wales:
This concrete monster the size of a main road plunges more than 330 meters to the valley below. It makes one of those terrifying Olympic ski jumps look like a speed bump. Standing on the public walkway at the top, looking down, is mesmerising and slightly nauseating. The water goes from looking-glass calm, over a lip, on to a shelf and then crashes down the slope, forming a beautiful foaming latticework all the way down:
It cannot be overstated that it is madness to contemplate any sort of trip down Llyn Brianne, but still it is used by kayakers (and even bikers).
These kayakers take the risk of being forced under water and thrown around like a pair of socks in a washing machine. Let's say it not a thing you want to plan for a vacation holiday.