We really enjoyed British History today. It was a circle of stone called Stonehenge. Nobody is quite sure who made it or what it was used for.
Some stones also mark events on the lunar calendar.
A lunar year is 18.6 ordinary years, and at least 6 lunar years needed to be observed to get the proper placement of the stones. That means that they had to have made observations for 111 years to complete a cycle necessary to correctly place the stones. Isn't it amazing that all this happened so long ago. The stomes are massive - over 20 feet high. Well, quite modern by Stonehenge standards, but still very old are the Roman baths at the town named after them, Bath, quite near Stonehenge.