Entered by a flight of forty steps,Underground passages, caverns, etc. of Greenwich and Blackheath, a lecture by J. M. Stone to the Greenwich Antiquarian Society, 26 February 1914 it consisted of three or more separate caverns joined to one another by tunnels. The first or main cavern is roughly circular and about in diameter. Leading from this is another about . There is a long, winding passage leading to a chamber which is about , varying in height from to , with a well of pure water, in depth, although in 1939 this was found to be , partly brick lined and quite dry.Caverns Found At Blackheath Air-Raid Shelters Ready Made, The Times, 27 Oct 1939, p. 5, col B At its lowest it is from the surface.
