Man-made underground passage in Corrinshigo (cremorne By)

No visible stone, no chamber, no ledge. A long shallow cut branches from the rath centre to its south-west gap, then turns west inside the bank. The ridge hides the shape, but the measurements leave little room for chance. Whoever made it did not build a chamber to be admired. They cut a route through solid ground, perhaps for water, perhaps for passage, perhaps for a warning carried underground. The earth kept the route secret. The numbers still point it back.