Stonehenge has recently been likened to Lego. However, it has two features that Lego doesn’t, and which make it cleverer than Lego: the tongue and groove joints which hold the ring of lintels together horizontally are rounded and the mortice and tenon joints that hold the lintels in place vertically are domed.

Joints used in the outer sarsen circle © Historic England (illustration by Peter Dunn)

As a result, the structure has a greatly increased ability to shift laterally following ground movement or settlement without catastrophic failure, hence prolonging the life of the monument (by millennia, we now know!)

So were those unique design features an attempt to make Stonehenge almost immortal? No-one can know but it’s nice to think so. It’s true that neither modern nor ancient carpentry employ rounded or domed joints so why else would Stonehenge be so different unless the builders were aware heavy sarsen would be in danger from ground movement and they were trying to future-proof their monument?