BOSTON (CBS) – The Boston skyline will be changing as construction is underway for what will be the tallest office building built in the city since 1984.

Mayor Marty Walsh held a groundbreaking Thursday for One Congress Street, the 600-foot tall, 1 million-square-foot office tower in the Bullfinch Crossing project.

Bullfinch, which is the site of the Government Center garage, covers a total of 4.8 acres over two city blocks. It will have six buildings for office space, apartments, condos, a hotel, shops and a 1-acre rooftop garden.

Walsh said that new office space is a positive sign for the economy.

“Seeing a need for additional office space in downtown Boston is key. A lot of cities struggling economically, they’re not building these buildings and they’re not seeing downtown grow. It’s good to see downtown grow as a job hub as well,” Walsh said.

The project will keep some of the Government Center garage available for parking, but the real solution to Boston’s parking concerns lies with public transportation, the mayor said.

“A lot of these new buildings we’re building, the lack of – need for parking is raising. That goes back to the MBTA issue – really making sure we have a system that is reliable and overachieving, not underachieving,” Walsh said.

Half the space in the home of the new office building will be home to State Street Corporation.

The project was designed by architects Pelli Clark Pelli. It is expected to be complete by 2022.