Sometimes it’s really hard to believe what are the abilities of a human. And they are really huge. Some things can sound even impossible.
Maybe today for you a marathon sounds impossible, but there are people who are looking even further. And those people have a name – ULTRARUNNERS. There are no boundaries for them. 50k? Easy. 100k? Fair enough. 200k? Now we are talking 
There are a lot of people who can run 100k, 200k, or even 1000k or 1000 miles and even more.
If you really want to try yourself in ultra marathon – look at this website: UltraRace.co.uk
There are quite a lot of different races from 50k to 860 miles(!).
I am sure, once you do an ultra, you will want more and more I know few persons who do them. Despite the fact that after 100k they feel terrible, they want more. It’s like a drug. And if saying the truth – I want to do an ultra too:) I love such challenges! Do you:)?