Nice fire road with gentle ascending grade to the reservoir. Great for kids and out of shape adults. If you bring kids, bring some fishing poles as the reservoir is rarely fished, so kids will have non-stop action there with the small fish. I have seen people swim there, although I am not sure how safe it is. This is the end of the Signal Knob trail noted elsewhere, but for those looking for something less epic, it is a pretty cool place to visit.
55 West of Front Royal, Left on Fort Valley Rd, Past Signal Knob parking about 8 miles to right on Boyer. Bear Right on Mine Mountain Lane, then right again on Fire Rd. Follow fire road until you get to a closed gate and park there. We were able to negotiate the fire road in a van, so it is not that bad - you just have to be careful to not bottom out on the crest of the road.
http://www.singletracks.com/item.php?c=1&i=3220