Historians Thought This Was a Medieval Site Linked to King Arthur. It Turned Out to Be a Mysterious Monument Built 4,000 Years Earlier https://www.smithsonianmag.com/smart-news/historians-thought-this-was-a-medieval-site-linked-to-king-arthur-it-turned-out-to-be-a-mysterious-monument-built-4000-years-earlier-180985470/ #science