"The caves -- ranging from Putnam County in New York’s Hudson River Valley to southern Maine -- bear many similarities to "beehive" chambers built in Ireland by ancient Celtic tribes, said Barbara Toomey, the Massachusetts coordinator for the New England Antiquities Research Association.
Here's another site about "America's Stonehenge." According to that site, there are 62 of these chambers in Connecticut, and yet I've never heard of one of them.
They give the example of the Gungywamp in Groton.
Besides containing beehive chambers and petroglyphs, the Gungywamp site has a double circle of stones near its center, just north of two stone chambers. Two concentric circles of large quarried stonesó21 large slabs laid end to endóare at the center of the site. Extensive fire burning on some of the slabs is apparent which leads many to believe it was an ancient altar. Nearby there are several large pillar stones and one boulder slab that have been carefully positioned along astronomical site lines.
I may have to take a road trip one of these days. Fortunately for me, I can learn more about it through The Gungywamp Society.