Scramble over—and under—30,000-year-old lava flows on this 10.4-mile loop at the edge of the Medicine Lake shield volcano. Bonus: Access dozens of backcountry lava tube caves and score some of the best stargazing in the U.S. Make sure to tank up on water before you start (a gallon per person per day), as this route is always dry. Begin at the Skull Cave parking lot (1) (ice lingers year-round in the nearby cavern, one of the park’s 25 enhanced with paths and ladders). Hike northeast across a sage-studded plateau on the Lyons Trail, an old homesteading road. The first unmarked cave appears on your right in .3 mile (2); look for a sinkhole with a faint trail you can follow into the rocky depths. Explore safely: Go in a group, bring extra lights, and protect your head with a bike helmet or bump cap ($6, visitor center).
Cross into the park’s wilderness area (3) and turn right onto the Three Sisters Trail (4) in another .6 mile. Wind past gravelly trenches where lava tubes have collapsed, watching the rock piles for obvious openings. At mile three, a log below a solitary juniper tree (5) serves as a lunch seat with a view of the 100-foot-high Three Sisters cinder cones to the north. Crunch into an area of old-growth juniper beginning at mile 4.2 (6). Find your campsite in this stretch of soft earth and shade. Note: At mile 4.5, the trail crosses into Modoc National Forest (7) where you need a permit to use your stove. After dark, take in the blazing night sky (“See This,” next page).
Day 2: Enter the national forest and continue through the junipers to a right turn onto an old jeep road .2 mile later (8). Follow the trail southwest to reenter the Monument at mile 5.2 (9). Two miles later, pass a field of smooth, ropy pahoehoe lava (10). At mile 8.7, bear right toward Indian Wells Campground (11). Across from site B-7 (12), find the gate to the Bunchgrass Trail. Continue northwest for .5 mile to the Missing Link Trail (13), then wind a dusty .7 mile north to the Symbol Bridge trailhead (14). From here, it’s a .1-mile road walk back to your car.
Get there From Klamath Falls, take OR 39 south 15 miles; go right on Merrill Pit Rd. In two miles, turn left on Stateline Rd. 161, then left onto Hill Rd. In 18 miles, go left on Lyons Rd. to the Skull Cave parking area.