This was a tough ride over advanced terrain due to elevation changes, and frequency and types of obstacles. Terrain is a mix of doubletrack fire roads and singletrack with several, extended rock gardens, rock outcroppings, technical climbs and descents, and the distance will probably vary considerably depending on how you build your loop. It is in the Appalachian foothills (Shenandoah Range), so expect some serious climbing (well, at least for us East Coasters). The saving grace is that a good portion of this was on the initial fireroad section, so establishing something of a cadence was not impossible (loose gravel and sand in the climbs is not conducive to great speed, necessarily). I would suggest getting a trail map; the blue trail is extremely advanced, very rocky, and would most likely require even the more advanced intermediate riders to dismount and walk portions (admittedly, it was tough just hiking it with the rocks, and in bike cleats). There are 4-5 creek crossings that were encountered, 3 of which were significant due to depth and large, slick rock. It was a fantastic ride, and took us about 4.5-5 hours to complete. Bring plenty of fluids, food (nothing around for miles), first aid kit, and full suspension (you could do this on a hardtail, but rear travel made this a lot more enjoyable I think). I will definitely do this ride again, and possibly take part in the Shenandoah Mtn 100 race next year (I'd do it this year, but considering the shape I'm in, it would probably kill me).
Trails Located in George Washington National Forest, approx 30 minutes north of Lurray Caverns off of Rt 340/522S from I-66W. From exit 6 off of Route 66W, proceed south and turn right at about 1.2 miles. There will be signs to Elizabeth Furnace Day Use area grounds. Also, check out www.more-mtb.org for more detailed directions. I'm not always the best person to ask for directions. :)
http://www.singletracks.com/item.php?c=1&i=935