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Auckland is an Industrial city-state in Civilization VI that was added in the Vikings Scenario Pack.
Strategy
Given the right map type, Auckland is arguably the most impactful and heavily contested city-state in the game. On water-dominated maps such as Archipelago, Island Plates or sometimes Shuffle and Fractal, Auckland is the one city-state on which to focus your envoy power because it can shift the power balance into its Suzerain's favor by turning every coastal city, from low growth with low 
Production, to a bustling industrial center, especially after the Industrial Era comes. Maritime civilizations such as Phoenicia or England, and especially the Netherlands, Indonesia, or Norway with their own infrastructure that improves coastal tiles, should definitely prioritize suzerainty of this city-state higher than any other one. Even if you are not playing as a civilization that prioritizes seafaring, as long as you settle a lot of coastal cities which are hampered by low Production, a combination of Auckland's bonus and Liang's Fisheries can definitely turn any city into a production powerhouse.
Civilopedia entry
When the Maori settled upon an isthmus in what is now northern New Zealand, they found the surrounding landscape full of fertile land, lush jungle, and dormant volcanos. Protected natural harbors on either side of the isthmus offered plentiful fishing and a base for war canoes ('waka taua'). The settlers named it 'Tamaki Makaurau'—roughly translating to "the maiden sought by a hundred lovers."
In 1840—nearly 500 years after the Maori arrival—the new British Governor William Hobson decided Tamaki Makaurau would make the perfect colonial capital of the very new New Zealand. He renamed it Auckland—roughly translating to "my patron is the Earl of Auckland, and I want him to think of me favorably when I ask for more money."
Though the capital later moved to Wellington, Auckland's loss of political prestige was more than compensated by its vibrant economy. Even its limited military skirmishes had financial resolutions: when a Maori tribe sought to attack the city in protest of their chief's arrest, Aucklanders settled the matter by handing over a substantial amount of tobacco. The opening of the Panama Canal in the early 20th Century further expanded Auckland's role as a vital stop in South Pacific shipping routes.
Trivia
- Auckland's city-state symbol are two sailing boats, referencing Auckland's nickname as the "City of Sails", due to sailing being an extremely popular pastime among Aucklanders.