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Australia entered the castle-building game relatively late. By the time its colonial governments began erecting fortresses, Europe had spent centuries experimenting with towers, battlements and increasingly elaborate ways to pour things on intruders. The Australian version was more pragmatic: coastal batteries, underground tunnels and large guns aimed at the sea, constructed in anticipation of foreign navies that mostly failed to arrive.
These monuments to defensive anxiety have now been assembled alongside thousands of their international counterparts on Castlemap, a free interactive atlas charting 7,093 castles, fortresses, palaces and ruins across 141 countries. The experience is dangerously simple. Open the map, select a pin and receive a photograph, exact location and concise history of the building in question, plus a founding date where one has been documented.
Australia contributes a modest ten fortresses, eight of which have documented founding dates. Its highest-ranked entry is Fort Denison, the tiny fortified island floating in Sydney Harbour between the Opera House and Garden Island. Known to the Eora people as Muddawahnyuh and later nicknamed Pinchgut, the rocky outcrop was once used as a penal site before being fortified from the 1840s. Its round sandstone Martello tower and low defensive walls now look almost decorative, giving the impression less of a military stronghold than a particularly feudal-looking waterfront wedding venue. The heritage site is currently closed to visitors throughout 2026 while conservation works are completed, but you can still admire it from land.
Next in Castlemap’s Australian rankings is Bare Island Fort at La Perouse, connected to the mainland by a footbridge with serious villain-lair energy. Built in the early 1880s to guard what was then considered Sydney’s “back door”, the fort later found a second calling as a filming location for Mission: Impossible 2. Visitors should note that Bare Island is currently closed for bridge works scheduled to continue until late 2027.
Third place goes to Victoria’s Fort Nepean, positioned at the tip of the Mornington Peninsula where Port Phillip meets the Southern Ocean. Once a critical part of Melbourne’s coastal defences, the fort fired the first shot of the British Empire in the First World War and the first Australian shot of the Second World War. Visitors can now explore its tunnels, barracks and gun emplacements, which is considerably more fun when nobody is firing from them. You can find your closest castle here.
The top 10 fortresses to visit in Australia
- Fort Denison, Sydney, NSW
- Bare Island Fort, La Perouse, NSW
- Fort Nepean, Mornington Peninsula, Victoria
- South Channel Fort, Port Phillip, Victoria
- Fort Scratchley, Newcastle, NSW
- Fort Macquarie, Sydney, NSW
- Fort Queenscliff, Queenscliff, Victoria
- Fort Lytton, Brisbane, Queensland
- Fort Glanville, Adelaide, South Australia
- Middle Head Fortifications, Sydney, NSW