Megan Singleton looks at some races for the truly diehard. Or the truly mad.
1. Tarawera to Kawarau
New Zealand plays host to the second extreme event of the year on the Ultra-Trail World Tour every February. This year's has just been, so you've got twelve months to prepare for the next one. Runners can choose to relay a mere 65km, 80km or 100km across our striking landscapes. One thousand people descend on Rotorua - including 300 from overseas - to run the race of their lives around four lakes, through forest and past waterfalls in this four-day event.
In its 12th year, the North Face Transgrancanaria races across the island of Gran Canaria and now attracts about 2500 walkers, runners and nature lovers who think nothing of a 100km walk to smell the roses - or whatever it is they smell on this Spanish island. They must be done in under 30 hours through rain, sun, mud and dust - so it's not just the elite who can compete. They also promise the course will be well signposted with plenty of aid stations.
The North Face 100 Australia race promises to be punishingly tough through the Blue Mountains National Park. The Aussies make no bones about it, this 100km race is for experienced athletes only and there is very little support in this remote terrain. Good luck.
4. United States
The Western States 100-Mile (note, mile not kilometre) Endurance Run is held in the Squaw Valley, California. It started in 1973 and runners climb nearly 5500m before descending 7000m to the finish line, passing through stunning high country, canyons and the icy waters of the American River before flopping into the welcoming arms of Auburn, California.
The Ultra-Trail du Mont Blanc has been called "the race of all superlatives". This 165km run winds through three countries. France, Switzerland and Italy all host the 2300 runners testing their mettle on the mastiff of Mont Blanc, starting at Chamonix. The event climbs about 9600m and must be completed in 46 hours. First runners are usually in after about 20 hours.