On a recent walk near where I live in Cambridgeshire, I stumbled across this feature on Iram Drove, Willingham: it's an Iron Age settlement or a medieval fort, bisected by a recent path.
Bing Maps Birdseye view shows this best. Although the vintage of the satellite imagery or aerial shots is unknown, the fort ring as well as ridge-and-furrow show well.
Hint: rotate clockwise and anticlockwise to see it better
(if you rotate twice and revert to map mode,
refresh the browser to return to the birds-eye view).
click on image and then search for:
iram drove, willingham, cambridgeshire
Search for the same on Google Maps and you'll find a 'teapot spout' on the eastern edge - that is simply a drainage ditch to empty what remains of the moat, in this water-logged region.