Holme I and Holme II are a pair of Bronze Age henges (monumental circles) built circa 2000 BCE. Holme I (dubbed Seahenge) is oriented towards the summer solstice and consists of an upside-down oak tree-trunk surrounded by a tight stockade of 55 timber posts. The two timber circles were exposed by the shifting sands of Holme-next-the-Sea beach on the north Norfolk coast in 1998.

What were their builders thinking of?

University of Aberdeen researcher Dr David Nance thinks he knows – and provides compelling evidence from ancient folklore to support his claim. They were built at a time of sudden deterioration of the climate, and constituted a scientific experiment to extend summer (…”science” such as it was in Bronze Age Britain).

The reasoning is intricate. Refer to the linked paper for details. Suffice here to say that it involves cuckoo cages, observation of the bird’s behaviour correlated with the solstice, plus an impressively precise dating of when the trees for the 2 monuments were felled (2049 BCE).