Trampoline parks are sprouting up all across the world. However, they all pale in comparison to Bounce Below - the world's biggest underground trampoline park that opened in the historic slate mining town of Blaenau Ffestiniog in North Wales, on July 3rd. Nestled in a massive cavern that is located inside a 100ft deep and 60ft wide former slate mine, it provides visitors with a bouncing experience like none other.