The tower is expected to run to 21 floors and to contain 148 market-rate apartments and 22 affordable ones. The 169,574-square-foot building’s studios, one-bedrooms, and two-bedrooms will range in size from 450 square feet to 1,200 square feet, the developer said.

Fortis is also promising a lot of amenities, including a roof deck and a top-floor fitness center with views of Boston Common and Boston Harbor.