Wiltshire, England, UK
c. 3000-2000 BCE
Built in several stages between about 3000 and 2000 BCE, Stonehenge is a circle of massive megaliths that weigh many tons, fit together perfectly, and are aligned with the stars.
Located in a village in Brittany, the Carnac Stones are a huge system of more than 3,000 prehistoric standing stones erected between 4500 and 2000 BCE.
Boasting a spectacular hillside location among olive and cork trees, this stone circle is the most important megalithic site in Portugal. Its 96 standing stones were arranged in an oval in 5000-4000 BCE.
Orkney Islands, UK
Located just outside the Ring of Brodgar, the Comet Stone is a heavy stone 1.8 m high. Lying at right angles to it are the remains of two other stones.
"The Pipers" are two standing stones spaced about 120 m (320 ft) west-southwest of the Hurlers, spaced 2.1 m (7 ft) apart. They could be boundary posts, although some scholars think they had an astronomical purpose. One stone is 1.7 m (5 ft 5 in) tall, the other 1.4 m (4 ft 9 in).