A possible souterrain

Various email today about underground chambers. Which reminds me of something like a collapsed souterrain I saw a few feet west of Rt 3 in Burlington. As I was exploring along there, I came across what looked like a stone-lined brook but, following it uphill a couple of yards, it turned out to be more like the entrance to a passage burial with a walled-off entrance, a collapsed ante-chamber and further deeper chambers, also collapsed, running in line up the slope. It was something like this cutting into a knoll:The upper part of the picture shows the features seen from 3/4 view. To the left is the stone-lined passage which gets deeper uphill - to the right in the picture. The passage is obstructed by a wall and uphill/beyond that is a collapsed structure with a hole hinting at deeper recesses underneath. Still further uphill and in line with that, are several depressions indicating other collapsed spaces. The lower part of the picture shows a "bird's-eye" view of the surface features.

Here is a view up the stone lined passage towards the walled off entrance. The dark behind it is where the roof is collapsed.
And here is a view down in the opposite direction from the top showing some of the depressions which suggest collapsed passage.

Finally here is another detail of the wall and collapse. Perhaps someone will want to check it out more thoroughly someday.
Backside of Rt 3 is not the sort of place you expect to find something interesting.