Hornby Lighthouse stands at South Head, watching over the entrance to Sydney Harbour. The red-and-white striped tower is modest in size, but the setting gives it real weight: cliffs, open ocean, and ferries and ships moving through the harbour mouth.
It is best visited as part of the South Head walk rather than as a standalone errand. Go in clear weather for the harbour views, and keep an eye out for whales offshore during the migration season.