The Grand Canyon Circuit offers a fairly unique Blue Mountains experience, passing through the shadowy recesses of a narrow canyon carved out by Greaves Creek, near the town of Blackheath in the upper mountains. There’s lush rainforest vegetation, tall and dark cliffs, as well as more open sections with dryer vegetation. There’s also excellent views from Evans Lookout of the Grose Valley, looking like a smaller, forested version of that other (slightly more famous) Grand Canyon. Evans Lookout is outside of the canyon, but a part of the circuit walk.
The walk is of moderate difficulty on a well marked track. On the day I took these pictures we combined this walk with the longer Rodriguez Pass for a full and varied day-hike.
The NPWS site has information on the walk. You can start on Evans Lookout Road, either at Evans Lookout itself (at the end of the road), or earlier on at the other end of the canyon, or indeed at a car park between these two spots. Either way you walk roughly parallel to the road on a constructed track for a while to complete the circuit.