Jack Cade's Cavern is a cavern, extending several hundred feet underground, in Blackheath, south-east London, England. It is located northwest of the Heath and southwest of Greenwich Park, mostly beneath the lawn of Hollymount Close. It was re-discovered in about the year 1780. They are also referred to as the Blackheath Caverns. The entrance was at the end of a row of small cottages called "Cavern Cottages" at the rear of Trinity Church on Blackheath Hill, (destroyed in WWII).