I'd never heard of an ultra-marathon race known as The Speed Project until I read an article about it at the BBC a couple of days ago.
The Speed Project (TSP) [is] an unsanctioned, unsupported 350-mile race from Los Angeles to Las Vegas via Death Valley.
It has no website, no "register here" button, no rules, no official route, no spectators and, until a week before, no official start date.
It's a "Fight Club" of the running world created in the mould of its founder. Before he found marathon running after moving to Los Angeles in the mid-2000s, Arend organised a rave night in a borrowed brothel in Hamburg's red-light district.
Despite the race's underground status, the start line is filled with some of the world's fastest athletes, and the biggest brands.
How do they get there? Well, that's a long story, shrouded in secrecy.
There's much more at the link.
Intrigued, I looked for more information, and found this video on YouTube. It's twelve minutes of very interesting viewing, if human extreme performance interests you.
I've never even remotely felt the need to challenge Mother Nature and/or myself in that way, and I guess by now I'm too old and decrepit to even think about it: but for some people, it's a way of life. Kudos to them for their determination and drive.