You've got to be pretty crazy to decide you want to run 26.2 miles. Like, that's hours of running, non-stop, with blisters on your feet and legs that must feel like lead.
If you're one of those people who wonder what on earth possesses runners to do the London Marathon, you'll be even more flabbergasted as to why people sign themselves up for these seriously tough-looking challenges.
However, they do take place in some beautiful places... so who knows, maybe you'll end up feeling crazy inspired (maybe).
Patagonian Expedition Race
Held in Wales, the swim is in chilly Lake Padarn, the bike course goes through stunning scenery (and hills), and the run goes up and down Mount Snowdon.
Apparently voted as "The World's Toughest Triathlon", there are half, full and double distances.
Yeah, you know what? We're quite happy with a 5k parkrun on a Saturday morning, thanks.