navy and are used as the home port facilities for about half the Royal Australian Navy's major ships. The wharves on the western side of the island have sufficient depth of water to berth the largest United States Navy aircraft carriers. Royal Australian Navy Heritage Centre The Royal Australian Navy Heritage Centre was opened in 2005 and is the official museum of the Royal Australian Navy. It is located in the Public Access Precinct of Garden Island: a section at the northern end of the island opened in 2002 that includes several heritage buildings and structures, historical relics, and naval monuments. The museum's exhibits include the conning tower from one of the Japanese midget submarines that attacked Sydney Harbour in 1942. The heritage precinct is isolated from the mainland by the naval and dockyard facilities, with public access limited to the Sydney Ferries service between Circular Quay and Double Bay, with the Garden Island ferry wharf at the north end of the island. Private pre-booked bus groups are allowed to transit through the naval base and dockyard to the heritage precinct under strict conditions. Other facilities Various workshops and other buildings on the island are under the control of the nearby HMAS Kuttabul naval base and are used for training and other logistical purposes. Proposed future usage Since 2000 the global cruising industry has been building a number of very large ships, some of which were too large to berth at the Overseas Passenger Terminal at Circular Quay, although modifications were made in 2014 to accommodate some larger vessels. Some large ships are permitted to berth at Garden Island's naval wharves, initially on an ad-hoc basis, followed in 2012 by an agreement to permit three cruise ships to berth per year. There have been calls for increased cruise ship access to the naval wharves, with some suggesting that the RAN should relocate entirely. Replacing the naval base with a cruise ship terminal would also free up the island to be redeveloped as harbourfront residential housing. The RAN and the Department of Defence have opposed these proposals due to the security risks and loss of capability the increased civilian presence would bring, and the enormous cost of replicating the existing capability at a new location (a 2013 defence white paper estimated a cost of over $6 billion, although naval personnel stated that this did not include the creation of support facilities