text: The Inco Superstack in Sudbury, Ontario, with a height of , is the tallest chimney in Canada and the Western Hemisphere, and the second-tallest freestanding chimney in the world after the Ekibastuz GRES-2 Power Station in Kazakhstan. It is also the second-tallest freestanding structure of any type in Canada, behind the CN Tower but ahead of First Canadian Place. As of 2023, it is the 51st-tallest freestanding structure in the world. The Superstack is located on top of the largest nickel smelting operation in the world at Vale's Copper Cliff processing facility in the city of Greater Sudbury.
  In 2018, Vale announced that the stack would be decommissioned and dismantled, beginning in 2020. Two new, smaller stacks were constructed under the company's Clean Atmospheric Emissions Reduction Project. In July 2020, Vale announced that the Superstack had been officially taken out of service, but would remain operational in standby mode for two more months as a backup in the event of a malfunction in the new system, following which the dismantling of the Superstack would begin. As of 2024, however, Vale has not yet announced the awarding of a demolition contract on the Superstack, and it remains unknown when demolition will actually begin; some have called for the stack to be left in place as a tourist attraction.
  In addition to further reducing sulphur dioxide emissions by 85 per cent, the decommissioning of the stack is expected to cut the complex's natural gas consumption in half.