Military installations were built during World War II to support the Auckland harbour defences and to house U.S. troops or store mines. The most visited remains of these installations is the old observation post on the summit. The northern shore of the island was used as a wrecking ground for unwanted ships, and the remains of several wrecks are still visible at low tide.
Baches (small holiday houses) were built around the island's edge in the 1920s and 1930s. The legality of their existence was doubtful from the start and the building of further baches was banned in 1937. Most have since been removed because of the ban and because the island has become a scenic reserve. However some 30 of the 140 baches remain as of 2010, and some are being preserved to show how the island used to be, once boasting a permanent community of several hundred people, including a good number of children. The buildings included some more permanent structures like a seawater pool built of quarried stones by convict labour, located close to the current ferry quay.
There are several daily ferries to the island from Auckland's main ferry terminal, currently run by Fullers. These allow day trips for the fit to walk to the summit and back, with stunning views of the harbour and city. An alternative to walking, a land train, co-ordinated with the ferry sailings, takes visitors to a short way below the summit. Accommodation on the island is limited to a small number of dwellings near the wharf, one of which is available for public hire. There are no campsites on the island, though there is camping at Home Bay on the adjacent Motutapu Island
