The Post had a nice story (and a video on line) about bike racing in Greenbelt National Park
The Greenbelt National Park Training Race Series takes place Wednesday nights for 16 consecutive weeks. The course is 1.4 miles on the perimeter road of the park. This is the 29th year of the series, making it one of the oldest training series races in the nation, and it's a hot destination for those who want to rack up enough races to advance to the sport's higher levels.
I knew there was racing in Greenbelt, I just didn't realize it was so close to my daily commute. Next year - all the races are over for this year - I'll have to stop by to watch a few.