The 12-room, 6,082-square-foot townhouse at 9 Walnut Street in so-much-to-see Beacon Hill last traded in January 2005 for $5,200,000. It has since been renovated, and it's back on the market through Coldwell Banker for $8,250,000.
The property is a relative pup for the neighborhood—it dates from only 1890—and comes with flourishes such as a roof deck with a retractable skylight and plenty of space for a home gym (as the current owners have it set up). There are also six fireplaces and an elevator.