Hobbs Quarry is a unique site containing rare exposures of a fossilised reef. For this reason, the site has been designated a Geological Site of Special Scientific Interest, and a Regionally Important Geological Site. The site is also a nature reserve owned by Gloucestershire Wildlife Trust.

The exposures in the quarry are of Wenlock limestone that formed in a warm, shallow sea during the Silurian Period. Today, the limestones contain abundant fossils of the animals and corals that formed the living reef. The trail through the quarry explores the different types of limestone and the conditions under which they were formed, along with the industrial uses of the limestones.