An area of 400 pits sits within the Norfolk landscape - but what is this field which resembles the surface of the moon?

First named Grim's Graves, Grime's Graves, near Thetford, is a Neolithic flint mine and Site of Special Scientific Interest which is a habitat for rare species of plants.

When one of the pits was excavated in 1870, it was identified as a series of flint mines dug more than 5,000 years ago.

The land contains Britain's only accessible prehistoric flint mine and a grassy landscape of more than 400 shafts, pits, quarries and spoil dumps is cared for by English Heritage.

In 2011, a dig revealed the area was bigger than first thought, and while it does not necessarily mean there are new sites to discover, could indicate a larger area of archaeological interest.

Thetford & Brandon Times: Inside Neolithic flint mine Grime's Graves, near ThetfordInside Neolithic flint mine Grime's Graves, near Thetford (Image: Newsquest)

Currently closed for conservation work, the Stone Age archaeological site is often open to visitors when they can descend nine meters by ladder to see black flint.

It is believed the Neolithic communities would have dug the pits seasonally and up to nine people would have been involved at a time.

Once they had finished digging one mineshaft, they would fill it back up with the materials they were removing to create the next pit.

The site was first excavated by Canon William Greenwell between 1868 and 1870 who confirmed it was a flint mine. Greenwell's Pit was excavated again between 1971 and 1972 and by the British Museum from 1974 to 1976 and has since then been left untouched.

A greenstone axe from Cornwall, antler picks and the skull of a bird were discovered in the pit.