Perched above Newcastle Harbour, this intriguing military site was constructed during the Crimean War to protect the city against a feared Russian invasion. During WWII the fort returned fire on a Japanese submarine, making it the only Australian fort to have engaged in a maritime attack. It's free to enter, but the guided tours are worth taking, as you venture into the fort's labyrinth of underground tunnels. Head to the shop for tickets or for a self-guided-tour brochure.