This pleasant park near Route 1 and the University of Maryland is a great place for running -- including distance running (which is what I've used it for). There are safe, clearly marked trails, a restroom, water fountain, benches and gazebos. The trail around Lake Artemesia connects with two or three very pretty running and bike trails that pass through Prince George's County. There are mile markers, although I always lose track of distance because some paths intersect and the numbering gets a little confusing. There are a number of ways you can enter the park. The only drawback is that if it's summer, and it's very hot, and you're distance training, there really is not enough shade. In that event, you may want to go to nearby Buddy Attick Park, which is not as nice, but does have lots of shading.