Huge technical downhill sections--used to be a mining quarry during the revolutionary war. Trails themselves are technically moderate, some rocks, roots, best of all are the mutliple huge downhills (we call these the fun parks). Good place to go when everywhere else is muddy, there is excellent water runoff. I highly recommend this spot if you are looking to play around or are looking for lengthy downhills on the trails that lead to lengthy uphills (up to 1.5 mile uphills).
Off of I-95 North, Exit 1A, Make a right at first light. Pass the Iron Hill Museum (on your right), and make the next right. This will take you to Iron Hill Park--park anywhere and jump on the various trails.
http://www.singletracks.com/item.php?c=1&i=116