The October 27, 1885 edition of the Boston Daily Globe announced that a shallow cave had been re-discovered in Arlington, Massachusetts–which even then was a fairly well-developed suburb of Boston. From the streets mentioned in the article, it is clear that this cave was somewhere in the current Menotomy Rocks Park, which in 1885 was still a wooded farm. Consensus in Arlington was that it had been the hideout of Michael Martin, the highwayman. This was based on the fact that some old firearms had been found within; and also some old residents swore that they had seen Martin entering the woods in the area.
Surely there could be no evidence of this cave still existing in the center of a metropolis? However, it appears to have been rediscovered by “JimP,” one of the contributors to the Rock Piles blog concerning stone sites in New England.
JimP had heard stories about a cave in the area, but apparently did not know the legend of Mike Martin. JimP found the cave opening had been mostly filled in with dirt, prohibiting access. [There is no reason to try–generations of local children apparently knew all about the shelter, leaving no artifacts.]
According to Michael Martin’s confession, he spent less than 48 hours in Middlesex County, so it is extremely unlikely that he used a rock shelter as a hideout.