Construction of two high-rises is expected to revitalize the 14.5-acre Christian Science Plaza, Boston's largest privately owned public space.

The First Church of Christ, Scientist announced on Jan. 23 that it has chosen Carpenter and Co., Cambridge, Mass., as master developer of a 20-story and a 50-story tower. Upon topping out, the taller tower would be one of the tallest structures in Boston.

The two project sites are situated on Belvidere and Dalton streets in Back Bay, south of the Charles River and Interstate 90.

The city has approved the broad scope of the project, and construction could begin by year's end at the plaza, which is bounded by the 60-story Prudential Center to the north, the Fenway neighborhood to the south and the South End neighborhood to the east. The new mixed-use towers will include rental apartments, condominiums, a hotel, ground-floor restaurants and retail space.

Prime Site, Strong Team

Richard L. Friedman, president and chief executive officer of Carpenter, said, "This site absolutely captivated us. It is a gem without peer" in Boston's Back Bay.

The design team will include Henry Cobb, a founding principal of Pei Cobb Freed & Partners, New York City, in collaboration with Cambridge Seven Associates, Cambridge. Cobb was design partner for I.M. Pei & Partners for Boston's John Hancock Tower during the 1960s and 1970s, when the church plaza was developed.

Cobb said his firm "welcomes the opportunity to participate in envisioning the important 21st-century addition to the architecture of the Back Bay."

Darren Messina, vice president of design and construction at Pei Cobb, said interviews will be conducted in the next few weeks to select the structural engineering team for the project.

Carpenter and its team will be responsible for designing, financing, constructing and maintaining the new buildings. The church will cooperate with the firm during the planning, design and public- review processes. After the necessary approvals and permits are obtained, Carpenter will assume full ownership of the property.