In the South of Spain there is still this megalithic construction dating from 3750 BCE.
https://en.wikipedia.org/wiki/Dolmen_of_Menga
When you are inside you notice a strange feeling, a mixture of claustrophobia and peace. It's built in front of a mountain that resembles the silhouette of a person lying face up, and probably the figure of the mountain was the reason for building a funerary monument there. An allegory of death.