Stony Batter is a historic defence installation at the north-eastern end of Waiheke Island, Auckland, New Zealand. It is sited within a 50-acre (200,000 m2) scenic reserve of the same name, owned by the New Zealand Department of Conservation (DOC). The park serves double duty as a historical (Category 1 Historic Place) and nature reserve, containing unusual rock formations, associated with an extinct volcano, three significant bush blocks and three concrete gun emplacements with an extensive tunnel system, reputed to be the largest in New Zealand. Counterbattery History Stony Batter was part of a counter-bombardment battery system progressively being installed in the Hauraki Gulf from the 1930s. Composed of various gun batteries, such as at Whangaparaoa, Motutapu Island and at Stony Batter, as well as having observation posts such at Rangitoto Island (command post) and Tiritiri Matangi Island, it was supposed to engage enemy naval forces entering the inner gulf. Ranges would have been too far beyond the line of sight (over 30 km, thus the need for a complex set of observation points and communication lines), as well as at least initially beyond the range of most enemy ships' ability to retaliate. While approved in 1939, construction was delayed for cost reasons until German raiders were sighted in New Zealand waters during 1940–1941, as well as the war entry of Japan in late 1941, suddenly turned it into a high-priority project. In 1942, the site on Waiheke was chosen, but it took until early 1943 before the Public Works Department was finally tasked with construction after other contractors declined the job. Construction began in October 1943, and it was initially thought that the battery would take 12 months to complete. Delays were caused by the remote location, which at first had no road access, and also by the fact that the project was kept in strict secrecy, requiring with a large degree of self-sufficiency during the construction period, complete with its own living facilities and machine shops. The new battery was generally referred to only as A2, to conceal its location. The tunnels and underground chambers were quarried by hand, with formwork for the walls and ceilings, then filled with concrete (reinforcing steel was not used due to shortages). Aggregate was obtained from the prominent rocky outcrops, giving Stony Batter its name. The tunnels and chambers were designed based on plans of the Tawa Flat railway tunnels project. The