have (something) down pat
to have learned or memorized something perfectly
I have the dance routine down pat.
Wonders of World
The Ring of Brodgar Orkney
The Ring of Brodgar, is on Mainland, the largest of the Orkney Islands, in northern Scotland. It is thought to be a lunar observatory dating back to 1500 B.C. The stone ring was built in a true circle, almost 104 metres wide. Although it is thought to have originally contained 60 megaliths, this figure is not based on archaeological evidence. Today, only 27 stones remain