The biggest

Location: 51 Commonwealth Ave., PH Unit, Boston Size: 8,976 square feet Price: $11.5 million Four condos were combined to make this mammoth 3½-level elevator penthouse.
Location: 51 Commonwealth Ave., PH Unit, Boston
Size: 8,976 square feet
Price: $11.5 million

Four condos were combined to make this mammoth 3½-level elevator penthouse.
(Pat Greenhouse/Globe Staff)
everyscape Check out the neighborhood