The Carnac Megaliths

Between 4500BC and 3300BC more than 3,000 standing stones were erected by the pre-Celtic people of Brittany. Some of the largest stones that currently stand in Carnac weigh more than 50 tons. Noone knows exactly why they did it.

Many of the stones have been destroyed or removed over time but here is an early painting of what it might have looked like

https://www.hurtigruten.com/must-read-articles/europe/exploring-the-megaliths-of-carnac-france/