Get full access to Outside Learn, our online education hub featuring in-depth fitness, nutrition, and adventure courses and more than 2,000 instructional videos when you sign up for Outside+ Sign up for Outside+ today.
Wolf Creek Trestle, Tillamook State Forest, Oregon
The Port of Tillamook Bay Railroad once spanned 88 miles and 60 trestles, but it never saw the profit its builders intended. Now, you can profit from their folly: This 10-mile out-and-back follows a section of failed railroad that includes tracks, trestles, and two eerie tunnels (open to the public). See nature’s reclamation for yourself when you traverse moss-covered concrete, storm-mangled rails, and tracks that have trees growing straight through them. Begin on the jeep track at Pennoyer Creek before heading northwest onto the tracks (they’re not active). Soon after the first tunnel (mile 1.8), you’ll hit a 165-foot-high trestle (take a look down past the steel girders to Baldwin Creek, a tributary of the Salmonberry River). Continue southwest into Tunnel 27, a dark, dank corridor prime for exploring, at mile 4. The trail dead-ends at mile 5; retrace your steps. Contactbit.do/TillamookStateForest
Deserted Pennsylvania Turnpike, Breezewood, Pennsylvania
Part of America’s first superhighway, this piece of I-70 was abandoned in the 1960s when the two-lane tunnels created miles of traffic. Today it’s a creepy reminder of an era past: Each tunnel has equipment rooms and offices still holding old relics (peek inside the rooms, but don’t go in). Urban explorers will like the elaborate graffiti. From the parking lot at U.S. 30 and Tannery Road, head east along the abandoned road to kick off this out-and-back (up to 7.3 miles each way). Reach the .7-mile-long Rays Hill Tunnel at mile 1 and the 1.3-mile-long Sideling Hill Tunnel at mile 6. Be sure to kill your light for a bit: It’s so dark you won’t be able to see your own hand, and the only noise is the staccato beat of dripping water. Turn around after Sideling. Contactgrouseland.com
Bennet Spring Natural Tunnel, Bennet Spring State Park, Missouri
We love the juxtaposition of man and nature on these tunnel treks, but sometimes the earth is her own best architect: A 296-foot-long natural tunnel, Bennett Spring is an impressive example of geology in action. It’s more than 15 feet high and 50 feet wide, thanks to Bennett Spring, which once raged through (now it’s just a mellow stream). Walk through the tunnel on a 7.5-mile loop from the Bennett Spring trailhead. Heading southeast on the blue-blazed path, reach S-shaped Bennett Spring Tunnel at the midway point. Hop across rocks in the drippy passage before linking back up with the trail on the other side. (Hot weather bonus: The dolomite passage is generally 15 degrees cooler than above ground.) Contactbit.do/BennettSpringStatePark