The Sydney Heads (also simply known as the Heads) form the two-kilometre-wide entrance to Sydney Harbour in Sydney, New South Wales, Australia. North Head and Quarantine Head are to the north; South Head and Dunbar Head are to the south; and, Middle Head, Georges Head, and Chowder Head are to the west and within the harbour.The Hornby Lighthouse is located on South Head and is Australia's third-oldest lighthouse.