Www.thisiscolossal. If you’re afraid of heights, caves, the dark, suffer from claustrophobia or vertigo, this might not be for you, but if not, a small Welsh town has the perfect subterranean adventure for you: the world’s largest underground trampoline. Just unveiled in Blaenau Ffestiniog, North Wales, Bounce Below is a network of trampolines and slides mounted to the walls of an abandoned slate mine at heights of 20 feet to 180 feet off the ground. Visitors are welcome to climb, bounce, slide, and jump in the netting amidst a technicolor light show. Tickets are available online and the space will open to the public July 4th, 2014. (via My Modern Met) 1x.com - Crystal Cave by Örvar Atli Þorgeirsson. - StumbleUpon. - StumbleUpon. Zion National Park-The Subway-3D Panorama. - StumbleUpon.