In the 10th century BC the ground level was much lower than today, increasing around 1mm per year as autumnal debris is added to the surface of the fens. This caused the structure to be covered up and preserved.
In the last century, draining of the fens has caused the surface to dry up and blow away which exposed the structure. Archaeologists are studying it and there is a well-organised visitor centre there with museum and exhibitions. One section of the poles are being preserved by replacing the cellulose in the wood with water carried wax impregnating of the wood over the years.
This technique is also being used to preserve Seahenge.