Maryland is full of rail trails, but only one of them detours around a tunnel because of who’s living inside it. Ride west from Big Pool and somewhere around mile 24 the pavement peels away toward the canal, sending you two muddy miles around a 4,350-foot hole in the mountain you’ll never get to see.
That’s Indigo Tunnel, the longest on the old Western Maryland line, now sealed off because eight bat species have moved in. One of them is the federally endangered Indiana bat, so the tunnel belongs to them now!
The trail itself runs about 28 paved miles through Washington County, from near Fort Frederick State Park west through Hancock to Little Orleans, with the 1830s Round Top Cement Mill ruins looming over the route just outside town.
It parallels the C&O Canal Towpath the whole way, so loop rides build themselves: smooth asphalt out, packed dirt back. Maryland DNR repaved 22.5 miles of it in 2024, and the surface is in genuinely good shape…