Bell's Grotto is a narrow canyon created by erosion from Tunnel Creek.
The old Wolgan Valley Railway ran through canyons & valleys for some distance upstream & downstream of Bell's Grotto. The canyon at this point was too narrow & too tightly curved for the railway & it was avoided by building the Glow Worm Tunnel.
When the railway was in use, passengers walked through Bell's Grotto when the weather was fine to avoid smoke from the Shay Locomotives.
Ben Bullen 8931-4S
Wollemi National Park (NSW)