The Sphinx, Warrimoo, Gibberagong and Murrua Link Tracks make for a shady 13km circuit walk, easily accessed from the Park Gates at the end of Bobbin Head Road. Three hours at a good pace is enough time to complete this walk, including a short tea break half way at the Bobbin Head picnic site. Park on Bobbin Head road, just outside the toll booths to avoid paying park fees. The Bobbin Head loop walk can be done in either direction (the map below is anti-clockwise). Walking clockwise allows for a warm up on the streets past the Sandakan Memorial and the easy going Murrua Link Track, before the very steep descent down to join the Gibberagong Track, finishing with a steady climb up the Sphinx Track at the end.
The total ascent for the loop walk is more than 500m. The climb from the bottom, at the junction of the Warrimoo track and Sphinx tracks, up to the top at the Sphinx memorial itself makes for a great time trial. Can you do it in under 20 minutes carrying a pack? How about 15 minutes?
Related nearby walks include the Gibberagong out and back route, the Sphinx and Darri Track loop and Hill climbing on the Sphinx and Warrimoo tracks. At Bobbin Head, Apple Tree Bay to Mt Ku-ring gai is another good 10km walk.
Wild Walks has detailed track notes on the Bobbin Head Loop, walked in a clockwise direction.