Revolutionary earthworks that survived by becoming a sheep pasture
In July 1776, straight after the American defeat in Canada, the army started fortifying this ground above Lake Champlain at Orwell, and kept building through the winter and into the spring. It did not hold. The Americans pulled out on the 5th and 6th of July 1777 and British and Hessian troops held the place until November. Afterwards it went back to being pasture for sheep and cattle, which is exactly why so much of it survived. It is a state historic site now, a National Historic Landmark since 1972, and the earthworks are still legible in the grass.
Other places on the map within a couple of hours of here.