Take a look at these pictures from the highest marathon in the world - around Mount Everest in the Himalayas.
And they're off! The event is held every year on 29 May to commemorate the first ascent of Mount Everest, by Sherpa Tenzing Norgay and New Zealand's Sir Edmund Hillary, on 29 May back in 1953.
Here's one of the runners, Francis Kersten, who'd travelled all the way from Belgium to take part. A local Sherpa Sudip Kulung, won this year's race in an incredible time of 3 hours, 52 minutes and nine seconds. Now that's speedy!
Participants are asked to be in Nepal three weeks before the race so that they can get used to the high altitude. Although the course is basically downhill, there are two steep uphill sections, which is why some runners use poles to help them balance.
This is the start line of the highest marathon in the world - Mount Everest Base Camp in Nepal. Runners from all over the world gather waiting for the race to start.
The marathon starts from Everest Base Camp (5,364m above sea level) and finishes at Namche Bazaar (3,446m above sea level) and as all marathons, it's a gruelling 26.2 miles long. The altitude makes running the race much more difficult than most marathons.