Megaliths

One or more large stones used primarily by ancient cultures as some sort of monument. The positions of the stones typically have some significance astronomically, such as marking Summer and Winter Solstice sunsets. There are over 1000 megaliths in Great Britain predating 1500 BC. The exact usage for these ancient stones is unknown. Stonehenge is the best known megalith.

There are several megaliths in the United States, including "America's Stonehenge" or Mystery Hill in New Hampshire and the Gungywamp in Connecticut.