Stony Batter, Nature reserve at eastern Waiheke Island, New Zealand

Stony Batter is a nature reserve on the eastern tip of Waiheke Island, New Zealand, made up of three bush blocks, concrete structures, and a network of underground tunnels carved through volcanic rock. The reserve sits on a rocky plateau, where open grassland meets dense bush and the remains of a wartime coastal defense installation.

During World War II, the site was built as part of Auckland's coastal defense network, with two naval guns installed to watch over the sea approaches to the city. After the war ended, the military abandoned the facility, but the underground structures were left largely untouched.

Stony Batter is one of the few places in New Zealand where visitors can walk through wartime underground defense structures that are still largely intact. The tunnels give a direct sense of what it felt like to work and wait underground during that period.

The reserve lies at the remote north-eastern end of Waiheke Island, where the sealed road gives way to a rough gravel track; the last stretch is best walked. The gun pits are open at any time, but the roughly one-kilometre tunnel system is seen on guided tours run under a DOC concession, so check tour times before setting out. Bring a torch and sturdy shoes.

The tunnels beneath the site were carved entirely by hand through solid volcanic rock, without any heavy machinery. Together they run for about 1 kilometer, connecting the different parts of the installation in a way that is still easy to follow today.