Mountain bike athletes Jono Jones, Olly Wilkins, and Mountain Bike Nomad rode downhill into the incredibly narrow tunnels of the abandoned Mežica Lead and Zinc Mine in Slovenia. This ride is known as the Blackhole trail and it is only for very skilled riders.
Black Hole Trail is a special challenge even for the most skilled mountain bikers. The trail runs through abandoned tunnels of the Mežica mine. From the day it closed down to the day they started setting up the trail, no human foot stepped into these tunnels.
via The Awesomer