The tallest office building currently under construction in Canada is now making an impressive impact on the Toronto skyline.

Work is in full swing at the site of a new 50-storey tower at 141 Bay Street, just across from Union Station, marking the second and final phase of developers Ivanhoé Cambridge and Hines' CIBC Square office complex.

The complex's second tower, now ascending into the downtown skyline, follows on the heels of a slightly shorter 49-storey first-phase tower completed at 81 Bay Street in 2021, matching its design from U.K.-based architects WilkinsonEyre working alongside local firm Adamson Associates.

Ivanhoé Cambridge/Hines

Unlike the majority of new-build towers in Toronto that use reinforced concrete as their primary construction medium, both towers at CIBC Square have utilized steel frames around a central concrete elevator core.

This construction method — much more common in office towers — allows the tower's slender elevator core to rise at a much quicker pace than the surrounding steel frame, visible in photos of the growing landmark.

Like the 49-storey tower to the south, the second phase building is being enclosed in a curtainwall cladding system that forms crystalline facades.

These facades are already shimmering in the sunlight, and will be further enhanced by LED lighting features once the project is complete.

The second phase will also feature an extension of the popular elevated park that opened with the initial tower, with the two sides together forming a new publicly-accessible space that bridges over the rail corridor.

And that's not the only bridge the public will gain as part of this project, with a shiny new pedestrian crossing in progress that will connect with Union Station to the west.

At a height of 241.4 metres (792 feet), the tower would stand as Toronto's seventh-tallest building if completed today. However, with a handful of even taller residential projects already well underway across the city, CIBC Square's prominence on the skyline will be overshadowed by other new builds.

That being said, a tower of this scale in an office market facing as many challenges as Toronto's is a huge statement of confidence from the developers, who broke ground on the tower in March 2021 — a very uncertain time.

In fact, the rising office tower may prove to be the last of its kind in the current development boom, being constructed amid waning demand for office space and runaway vacancy rates in the downtown core. Other high-profile office tower projects in the vicinity have been placed on hold and may not come to fruition for years or even decades.

Outside of the office classification, there are currently only five buildings under construction in Canada that will rise taller than the second phase of CIBC Square, four of which are in Toronto and one in Mississauga.

The tallest of the bunch is under construction just a few blocks southeast of the CIBC Square site, at 1 Yonge Street. The quickly rising Sky Tower at Pinnacle One Yonge will eventually reach a staggering height of 345 metres, approximately the same level as the CN Tower's main observation deck, becoming the tallest building in Canada once complete.