Construction work has officially begun on a new supertall skyscraper in central Toronto. Designed by high-profile British architecture firm Foster + Partners, the mixed use building will rise to a height of 306 m (1,003 ft), making it Canada's tallest skyscraper once complete.

The One, as it's officially named, will have a total floorspace of 79,924 sq m (860,294 sq ft), spread over 85 floors. Structurally, it will consist of a glass curtain wall, broken up by a structural framework finished in champagne bronze. The building's exterior appearance will also be interrupted by horizontal bands at regular intervals, which denote mechanical floors containing electrical and utility services.

The first nine floors will be given over to retail stores, cafes and restaurants, arranged around a 60 m (196 ft)-tall atrium. The rest of the skyscraper is mostly taken up by residential space, with its uppermost floors featuring duplex penthouses with sweeping views of Lake Ontario.

Resident amenities will include winter gardens, a sky lobby with spa, fitness facilities, library, and a large terrace.

Though it will be Canada's tallest skyscraper once complete, The One will be Canada's second-tallest manmade structure, as Toronto's iconic CN Tower rises to 553.3 m (1,815 ft). Completed in 1976, the communications and observation tower was the world's tallest freestanding structure from completion until it was surpassed by the Burj Khalifa.

To put The One's size into perspective, the 1930s-era Empire State Building south of the border in NYC is larger at 381 m (1,250 ft), not including spire, while SOM's recently-completed One World Trade Center, also in NYC, tops out at 541 m (1,776 ft).

The One is expected to be completed in 2020.

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