Listen to Aubrey Manning’s ‘Unearthing Mysteries’ programme on the tri-radial cairns of Northumbria.
About 20 have been found (some are at Lordenshaw. The three arms of the cairns are aligned in the same way; one pointing north and the others at 140 and 240 degrees (SE and SW). That means they could be pointers to the mid-summer and midwinter sunrise and sunset. It’s thought that they’re Bronze Age.