Depends on what you mean by 'learn from' too

There are the truly fabulous from the air Thornborough Henges, (under quarry risk still) that can only be viewed from the road and are as important in our heritage as Stonehenge, but visually not as effective from the ground since the land is private but two are very close to the road. They are between Ripon and Masham. There's the Devils Arrows at Boroughbridge, lots of cairns, but if you want a fascinating place that's not prehistoric then try the Druids Temple at Masham. Built in about the 18th century and made to look like a stone circle, complete with altar, cave like area behind it with great luminous green moss D: it's used annoyingly by people today who think nothing of lighting campfires there

That's a great place.
Then there's Sutton Bank where the iron age encampment was, there's no sign of it now to the normal eye but the views are dramatic and you get a real idea of why they built it there. Plus below that is the Kilburn White Horse, created in 18something based on chalk hill figures and occasionally turned into a stallion or zebra

All these are North Yorkshire, there are plenty more