The Coal Hole to the north-east of the Great Conservatory is out of sight of the main path through the Rockery. Once the coal reached the coal hole, it was taken in small wagons along the underground railway.
Although the exit to the Coal Tunnel was always open there was a blockage further up the tunnel. In 2002, filming at Chatsworth encouraged an exploratory dig to assess the blockage. Clearing of the Coal Tunnel and Coal Hole revealed that it had been filled in with rubbish including plants and pots from when the Great Conservatory was destroyed. After the tunnel was excavated, the tracks were removed and handrails and lighting were installed. The Coal Hole and Tunnel was opened to visitors in 2003.