Impressive caves, some with supportive brick entrances but the majority are in their original stone form. There are over 20 miles of mysterious caverns and passages which have been hewn out of the chalk over a period of 8,000 years. Caves are not natural caverns created by running water, but passages carved out of the hillside by men in search of chalk and flint. The caves today consist of three separate workings: outer, inner and remote. The third working can only be entered through the inner section. The shape of passages in each set of caves is different. The caves became a nightly underground shelter for over 15,000 people during the Blitz. There are several reconstructions showing what life was like in the tunnels during the war.