Never mind Viagra -- every lap around the mountain bike trails in Quiet Waters Park will help your cojones get bigger. When you first start going around the 5.5-mile loop, you can take the novice route, which is full of cheat chutes that let you circumvent the steep drops and hard parts. If you crash on this trail -- which is well-marked with green signs -- well, you'd be pretty pathetic, but you'd fall onto a layer of pine needles that feels like a bed of Charmin. As soon as you become more confident, start tackling the harder trails in all their root-, rock-, and sand-bound glory. One section of single track is covered with tree branches and feels like you're tunneling through a cave; another section forces you to make tricky drops while trying not to fall in the lake. In addition to the roller coaster-esque cruise around the park, there is a trick area with teeter-totters and jumps for all levels of ability. Wear a helmet, keep at it, and soon you'll be swapping pictures of your yard sales and bruises with the folks at Club Mud -- a mountain-biking group that brings machetes to the park each month and keeps the trails in shape. Once you've mastered the trails, join the Mudders for some laps -- at night!