The 11-room, seven-fireplace Unit 3 at 257 Commonwealth Avenue in Back Bay is part of a subdivided mansion dating from the late 1880s (it was broken up into six units in 1985).
The 5,930-square-foot spread as such has a lot of elegant touches, including spacious entertainment rooms and an elliptical staircase. The four-bedroom, three-bathroom condo also comes with a 900-square-foot deck. There’s a keyed elevator, too, and two garaged parking spaces.
Understandably, given this scope and the location (it overlooks the Commonwealth Avenue Mall), Unit 3 is not coming cheap: It’s asking $10.5 million through Marsh Properties.