If you've ever pondered the limits of what's actually rideable on a mountain bike, there can't be many diehard descenders who have considered riding an underground mine shaft. But after being first explored on two wheels by Anej Strucl, that's exactly what Jono Jones, Olly Wilkins and their cameraman have just done.
Dubbed the 'Black Hole Trail', the Helenski tunnel is part of an abandoned Slovenian lead and zinc mine network with 1,000 km of tunnels, so it would be easy for the riders to get horribly lost underground. Handily, Anej leads a team of MTB guides, so they'd already opened up the tunnels previously unused for 25 years. His team had marked the best route and added concrete and metal bridges to turn the passages into a bonefide bike trail. As you'd expect though, being a old mineshaft there are some properly steep sections and super tight tunnels to negotiate at speed.
The Black Hole Trail is not just for pro riders though, it can be ridden by skilled MTB mortals too. Bikenomad in Slovenia will guide you through the tunnels, the trip takes around four hours and costs €75. For more, check out bikenomad.com.