Image courtesy of Stantec

Boston Properties has started construction of the tallest building in Cambridge history, the 121 Broadway residential tower slated for completion in 2027.

The 37-story, 439-unit tower will cost an estimated $598 million, Boston Properties estimated in its first quarter financial statement.

The project is part of the Boston-based REIT’s Kendall Square development that also includes the 290 and 300 Binney St. office-lab towers, which are under construction.

Boston Properties redesigned the residential portion of the project in 2021, replacing two shorter apartment buildings with the single tower to make room for an Eversource electrical substation.

The 450-foot-tall tower will include a 37th floor sky deck and sixth-floor outdoor terrace, according to architects Stantec. The project reserves 20 percent of the units as affordable and 5 percent for middle-income households.

Currently, Cambridge’s tallest building is Massachusetts Institute of Technology’s 29-story graduate housing tower on Main Street.

121 Broadway’s distinction could be short-lived as MIT moves ahead with redevelopment of its nearby Volpe Center redevelopment. The master plan includes one residential building approved for a 456-foot height.

Boston Properties’ existing local apartment properties continue to fetch premium rents, according to financial data released this week.

Its Hub50House at The Hub on Causeway, a joint venture with TD Garden owner Delaware North Cos., is 94-percent leased with average rents of $4,366, up nearly 5 percent from the previous year. Average monthly rents are $4,257 at The Lofts at Atlantic Wharf in Boston and $3,154 at the Proto Kendall Square property. 

Boston Properties executives said in January they planned to move forward with several approved multifamily developments, but would hold off on groundbreakings of new office projects without substantial tenant commitments. In April, Boston Properties signed a 90-year lease with the Massachusetts Department of Transportation for the MBTA Back Bay station redevelopment that includes a 668,000-square-foot office tower on a portion of the station garage site.

In Kendall Square, the office-lab tower at 290 Binney St. secured a 570,000-square-foot lease with AstraZeneca in 2022, while The Broad Institute signed a full-building lease for the 240,000-square-foot 300 Binney St. in 2022.

BXP Breaks Ground on Cambridge’s Tallest Building

by Steve Adams time to read: 1 min