The camp is 250x250 meters so a lap within the protective walls of the camp measure 1k, meaning that to run the full marathon they had to run 42 laps. There were several different categories/races - a relay, a half marathon, the full marathon and even a 'lazy marathon' which means you could walk or run the 26 miles spread out on several occasions during a week. There was a hydration station that they passed on every lap, keeping the participants well hydrated. The winner, Sven Thelin, fininshed the race in 3:28:25 despite the temperature reaching 30C!
Here are some pictures from the race, taken by Kajsa Norman/FS24 (here's the link to their blog) and borrowed from the Marathonblog at SvD:
Relay changeover for the winning team (2:48:01)
The winner, Sven Thelin
Claes Jeppson finishing the halfmarathon
The winning relay team