Delaware North and Boston Properties yesterday marked the groundbreaking for The Hub on Causeway, its newly named, ?1.5 million-square-foot-plus development on the old Boston Garden site that is set to transform the North Station area.

The mixed-use development will have retail, office and residential space, and a 260-room hotel on the 2.5-acre Causeway Street site next to Delaware North’s TD Garden that opened in 1995 and will be expanded as part of the project.

“This development will be the crown jewel of this neighborhood revitalization,” said Charlie Jacobs, CEO of Delaware North Boston Holdings.

The Hub’s largest supermarket, a 60,000-square-foot Star Market, will be built in the first phase of the project that will include some 210,000 square feet of retail and restaurant space in total. Los Angeles’ ArcLight Cinema will open ArcLight Boston, a 60,000-square-foot movie theater complex with 15 screens.

“A supermarket in this neighborhood is needed,” Mayor Martin J. Walsh said, noting that the entire project will have a “transformative effect” on the neighborhood and add amenities for the community that remain after fans leave TD Garden. “It’s also going to bring much-needed workforce housing.”

The Hub on Causeway’s 175,000 square feet of “creative” office space will be work-loft spaces. There also will be 540 underground parking spaces connected to the existing North Station garage and 10,000 square feet of outdoor space that will include a new entrance to TD Garden and North Station.

TD Garden’s third to ninth floors will be expanded by 64,000 square feet. “You will be able to look through the entrance all the way up to level nine,” Jacobs said. “We will be increasing the retail, food and beverage, and guest experience.”

Jacobs couldn’t give an estimated project cost, but the Boston Redevelopment Authority put it at $950 million when it green-lighted development plans in 2013.

When its first phase is completed — set for late 2018 — there will be a new underground connection from the North Station commuter rail to the MBTA’s North Station Orange and Green subway lines.

The project’s second phase will bring a 38-story, 440-apartment tower and the 10-story hotel to Causeway Street, and a 21-story tower, 525,000-square-foot office building will complete the project.

“Frankly,” Jacobs said, “once they begin the process … this will go up pretty quickly.”