A beautiful Tree Fern filled grotto, is part of Tunnel Creek and is located on the southern side of the Glowworm Tunnel. This grotto by passes the tunnel. It was also referred to as Penrose Gorge. Eardley, G H. and Stephens, E M. The Shale Railways of NSW, 1974, p. 136, record, "The more hardy adventurous passengers left the train during the watering operation and walked the narrow footpath through the beautiful Bells Grotto." Ref: Deane, Henry. The Wolgan Valley Railway - Its Construction, 1910, reproduced by the Australian Railway Historical Society, 1979, p. 13, shows a map with Bells Grotto.