Eight years ago, the sprawling campus of the old Boston Specialty and Rehabilitation Hospital was largely dormant and - in places -crumbling. The shuttered Foley building - the old hospital's battleship building - was a foreboding presence along River Street.

Today, after an investment of more than $80 million in construction costs, the 27 acre campus is buzzing with new homes, streetscapes and amenities.

Trinity Financial will celebrate the completion of the final phase of the job with an all-day community party Saturday. The event will run from 11 a.m. to 3 p.m. at the River Street campus.

Mattapan Heights III is a 73-unit apartment complex that includes 12 units in the old Children's Ward building at the rear of the campus. Next door, 61 new apartments are housed in two new buildings. Trinity officials say all of the units are now fully leased. The third phase has also resulted in a new home for the Mattapan Adult Day Health program, which had been housed nearby on the old hospital campus for the last 30 years.

"It's a stunning, state-of-the-art facility. When you come in, you feel at home," says Maggie Shea, RN, the program director of the Mattapan Adult Day Health program. "It's not that old institutional style setting. We do the same thing in old facility, but now it's a much more comfortable, professional setting.

Activities on Saturday include a welcoming ceremony that begins at 11 a.m., live musical entertainment, tours, and a raffle that includes a $500 grand prize. A children's activity zone will include a moonbounce, face painting and games for the kids.