Picture 2 of 2.
Trethevy Quoit on Bodmin Moor is around 5,5000 years old (dating back to the Neolithic period, 3500 BC). The box shape of stones was originally the centre of a mound, probably holding a burial, over time the mound has worn away.
This picture shows the whole structure. To give you an idea of size I could stand up in the higher end of the structure, at the far end I had to bend.