Consisting of concentric circles of stone surrounded by a moat (called a "henge"), Stonehenge was constructed in several stages over thousands of years.
But their surfaces bear witness to homely labor: Topping the tallest stone, once part of a trilithon, is a tenon—half of a mortise-and-tenon joint borrowed from woodworking.
Bombproof -A hold or anchor that is thought to offer the utmost security; for example, a top-rope anchor around a large, stable tree trunk or immovable boulder.
Another form is the menhir, a simple upright stone usually placed with others to form a circle, as at Stonehenge and Avebury in England, or a straight alignment, as at Carnac in France.