Map showing extent of Doggerland, a vast territory in northwest Europe that was above sea level 16,000 years ago, and the territory's diminishing size as ice melted and the North Sea rose. Illustration by Claus Lunau/Science Photo Library.
Via https://sciencemastodon.com/@ebender00/113606996477811407
Also, a henge isn't a stone circle. It's a ring-shaped earthwork. What we think of as Stonehenge is a ring of Megalithic standing stones (not all standing stones are in a circle incidentally) in the middle of a henge.