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Photo: Victor Lucas

No one can deny that mountain biking is a gnarly sport in its own right.

However, when you throw in four-inch singletracks overlooking 2000ft drops with loose terrain, tree roots and boulders the size of small houses, it starts to enter a whole new levels of sketchy.

We've scoured the globe for the most dangerous, technical mountain bike trails around - from the treacherous roads of Bolivia to the Atlantic cliff tops of Ireland.

This is by no means an exhaustive list. Utah alone could practically fill the entire rundown alone! We have just selected a few of the sketchiest trails we've come across.

So, will you be avoiding them or adding them to your bucket list?

[part title="Yungas Road, La Paz, Bolivia"]

Photo: teacherontwowheels.com

Back in 1995, the Yungas Road was officially entitled the most dangerous road in the world. An average of 200 to 300 travellers die here each year - including 18 cyclists since 1998.

It's made up 43-mile single track road leads from La Paz to Coroico, Bolivia with 2000ft cliff drops and no guard rail.

Combine this with heavy rain in monsoon season and risk of rockfalls in summer, and you've got one sketchy road!

Why is it so popular with mountain bikers? Well, there's a glorious 40 mile stretch of solely downhill riding with only a tiny uphill part.

If this isn't enough to scare the bejeezus out of you, then try the Ayma trail near La Paz. Check it out in the video below - just ignore the terrible music and focus on the insane terrain!

[part title="Cliffs of Moher, Ireland"]

Photo: Victor Lucas

Swiss world champion and fully-fledged nutter Hans Rey decided he wanted "ride all the cool biking trails and spots in Ireland and to visit a few pubs along the way".

Obviously that means something slightly different to Hans than it does to you or I, as he chose the craggy Cliffs of Moher.

The trail narrows to just four inches wide with a whopping 600ft drop straight down into the North Atlantic. Strong winds have been known to sweep people off the rocky edges. Even with slightly foggy heads from one too many pints of Guinness the night before, they managed to avoid falling to their death. Would you give it a go?

[part title="Porcupine Rim, Utah, USA"]

Photo: Trevor at MTBR.com http://forums.mtbr.com/idaho-montana-wyoming/yay-moab-284028.html

Deep in the heart of the MTB mecca of Moab, Utah is this hell-raising trail appropriately named Porcupine Rim.

Those looking for a technical ride will not be disappointed. Expect eight miles of dust road and spectacular canyon views before you career three miles down the sketchiest singletrack of your life. Think two-foot gaps, loose sandy sections and exposed cliffs that fall away into the Colorado River.

But it's not the sheer drops that pose the most risk to riders - dehydration is the biggest killer on this trail. It is the desert after all, where temperatures often reach 38 °C. Back in 2005, a 15-year-old girl died from dehydration on a family bike ride here. So remember to take a lot of water with you!

[part title="Ötschergräben, Austria"]

Nothing like a super-narrow singletrack to get your heart pumping. If you haven't seen this video yet, then it's about time you checked it out.

Three German lads - Jello, Loschi and Pauli - crossing Indiana Jones-style rickety bridges and living on the edge (quite literally!). Lose your balance and you'll be tumbling into that ravine quicker than you can say "wienerschnitzel"...

[part title="Garbanzo, Whistler, Canada"]

Chris Kovarik taking on the gnarly root-strewn Garbanzo trail. Photo: Dave Trumpore

You're going to need some strong forearms to cope with one of Whistler's gnarliest sections.

As you enter the Garbanzo trail, there's a fork pointing left to intermediate and right to expert trail. Don't be fooled into thinking this is going to be a ride in the park.

Tree roots the size of your thigh, giant boulders, huge drops - and that's just the opening section. If you fancy getting your shoulder popped back into place afterwards, then take the expert trail and hope you don't live to regret it!

[part title="Maritime Alps, France"]

With the snow finally melting away across the French Alps, this could be one to try this summer.

Towering ridge lines and hairpins bends before the hillside drops away at 45°. It can only be the Maritime Alps. Dirt Magazine's James McKnight hits up this sketch goat ledge a few year ago. What did he think?

"I don't know how to describe the trails up in the Higher Maritime," says James, "but some of the words that come to mind are 'inaccessible', 'slightly treacherous', 'technically demanding' and 'discreet'". Hmmmm...

[part title="Lunch Line and King Kong, Utah"]

There's a reason why this video has nearly 2 MILLION views - it's pretty bloody gnarly!

Downhill rider Sage Cattabriga-Alosa must have balls of steel to take on some of these gnarly cliff tops. The rock practically crumbling away beneath their tyres!

Sadly, the quality of the video is kinda dodgy, but the content is unbelievable. Watch out for the insane drop at 3.29!