Sports fans and North Station commuters will start to see big changes next month as the TD Garden unveils a 50,000-square-foot expansion and renovation, including new concessions, a members-only social club and a new entrance on Causeway Street.

TD Garden owner Delaware North Cos. is spending $100 million to upgrade the 23-year-old arena as part of The Hub on Causeway redevelopment project, a partnership with Boston Properties that broke ground in January 2016.

Two escalators in the new glass-canopied atrium will bring Garden visitors and commuter rail passengers to the second level event entrance, while a new pedestrian tunnel beneath Causeway Street will open next month connecting North Station’s commuter rail terminal to the MBTA Orange and Green lines.

Upgraded concessions include the membership-only “Boston Garden Society” with private entrances and dedicated elevators. Memberships start at $1,200.

The project also includes a 500-space expansion of the North Station garage, which is completed.

Additional concessions will be added to the arena next season, including “The Rafters,” a members-only “party deck” overlooking the court and new luxury boxes for groups of 20 to 200.

The $854 million Hub on Causeway project is adding 1.9 million square feet of development to the property including an office podium building and tower, 400-unit apartment tower, 250-room hotel, ArcLight Cinema, Star Market and a 2,500-capacity live music venue.

Online security firm Rapid7 leased the office podium building in November 2017. Verizon has leased a majority of the new office tower for a relocation and expansion of its East Coast Innovation Center, currently located in Waltham.