Grimes Graves

Grimes Graves is the visible remains of a complex of flint mines. Several hundred shafts were dug to allow the high quality "floorstone" flint to be mined. The pits were backfilled with spoil from nearby shafts, leaving a pitted surface to the ground, often referred to as a "moonscape"

An excellent description of the site can be found on Wikipedia.

Access

The site can be seen (through a fence) from forestry tracks. To explore the surface features, and to go underground in an excavated mine it is worth paying the entrance fee. Details of times and costs are on the English Heritage website.