Old Mans Valley sits in a natural valley between the quarry void and Peats Ferry Road. Steep slopes on the valley sides feature natural bushland embankments, as well as embankments created by past quarrying and landfill operations.
Among the bushland in the valley is Blue Gum Diatreme Forest, a critically endangered ecological community of which only two percent is remaining.
The most popular feature in the valley is the mountain bike trail which was created by Hornsby Shire Council.
The valley also includes a number of heritage sites, such as the State heritage-listed Higgins Family Cemetery that is the final resting place for a number of the area’s early pioneers.