From Pagosa's website...
Blue Creek 4x4 Trail
This is a fun ride that doesn’t go anywhere important. The trail is a “roller coaster” type ride with enough challenge to keep you awake. The trail is about 13 miles long and connects The Blanco Road, 7 miles south of Pagosa to the Buckles Lake Road near Chromo, Colorado. There are some shorter 4x4 trails off the main route to try as time allows.
East Fork / Elwood Pass (FR 667)
This 4x4 trail is the “real thing” and the best off-road experience in the Pagosa Country area. It climbs about 18 miles to the top of the Continental Divide and meets with a forest access road just east of the divide. Once on top there are a lot of interesting things to do in the Elwood Pass/Summitville area.