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The milestone will be celebrated with a series of events that will tie in with the biennial 10-day Dunedin Heritage Festival run by the Southern Heritage Trust.
Celebrations begin tomorrow night with a military-themed launch at the Royal Albatross Centre.
For 10 days it will celebrate 30 years of Fort Taiaroa tours with free guided jaunts around the area.
Other events include Fletcher House tours to recognise 25 years of the Edwardian villa being open to the public, a Glenfalloch Gala Day on Sunday and a Harbour Heritage Photo Contest.
The trust was created by a small group of jaycees as a way to revitalise Dunedin.
Co-founder Bill Dawson, who remains one of its trustees, said the idea came after the release of an economic survey of the town.
"We discovered Dunedin was really in a bad shape and so we said `What can we do?'.''
Initial plans of creating a "Disneyland'' in Woodhaugh Gardens proved to be fairly unrealistic, he said.
"At that stage, the owner of Glenfalloch Gardens wanted to sell to us. He couldn't find a buyer anywhere in the city.''
The trust was then created to buy the gardens.
Fifty years on, its achievements were greater than he expected, Mr Dawson said.
"We started with no money and no credibility and just an idea. What we've achieved is quite remarkable.''
There was "unlimited scope'' for what the trust could do in the next 50 years, he said.
"We could double the operations of the peninsula tomorrow if we had the money.''
Co-founder Laurie Stewart said the trust's greatest achievement was its developments at Taiaroa Head.
"The albatross colony proved to be a great asset, and the blue penguin development is going very well,'' he said.
General manager Robyn McDonald said the trust had many upcoming projects and would continue its important work educating schoolchildren about conservation.
"We're going to go from strength to strength.''
It was also opening a "city presence'' in lower Stuart St, in the Otago Daily Times building.
The space, expected to open late this month, would be an information zone and booking centre, and would also hold the archives of Fort Taiaroa, the site of the Armstrong disappearing gun.
The archives would be available to the public on request.