Howell Cave is a large, but shallow, opening in the limestone cliff just upstream from McMahons Mill. It’s a pretty easy find because the stream exiting from the opening is easily spotted due to the fact that the canal doesn’t resume for another .62 miles. The area between the mill and Lock 41 is made up of a long line of cliffs and is actually an extension of the Big Slackwater section of the C&O.
The cave is relatively open and doesn’t contain much of a roof, unlike Dam 4 Cave and some of the others in the vicinity of Snyders Landing. It’s a beautiful place, except for the usual graffiti and the fact that it is apparently regularly used by campers. There is a relatively large pile of campfire embers at the base of a faux chimney of sorts, and it’s a shame that this tribute to the power of water can’t be kept in more of a pristine condition.
Perhaps the most impressive feature in the cave is a fairly large stream that emerges from a hole on the lower left side. According to Thomas Hahn, it is believed that this is the same stream that enters into a sinkhole approximately 700 yards to the north. If so, the reappearance is brief, as the water spills over a small fall before running under the towpath and emerging into the Potomac. Today, the river was running high, and the stream actually entered below river level and created a “bubbling sensation” at the surface.