I was curious so I did some digging. Turns out there a few I was able to find that can be reasonably attributed to ancient humans. I found this site [1] that mentioned a name which turns out has a Wikipedia page [2] that talks about a stone chamber that was likely built in 2000-770 BC as an astronomical calendar.

[1] http://planetvermont.com/pvq/v9n1/megaliths.html

[2] https://en.wikipedia.org/wiki/Gungywamp