I've been out there when I worked at Frontier Airlines and got a tour of the maintenance facility. There's a sod farm and not much else out there. DIA's land area according to the news is large enough that supposedly Chicago O'Hare, JFK, Newark and one other airport could all fit inside. It's very strange.Those familiar with DIA know that the runways are not easily accessible from any streets, roads etc. They are more or less in the boonies. The airport is huge from a land standpoint. Lots of open space around all the runways. This person had to go well out of their way to get on a runway at DIA, you wouldn't accidently stumble on one. To be walking down the middle of an active runway is even more bazar.