Beacon Hill has long been one of the most historic and luxurious neighborhoods in Boston. In fact, the 18th century architect Charles Bulfinch—who designed the Massachusetts State House—originally planned for landscape of the area to focus heavily on freestanding mansions, according to the city of Boston. 

Those mansions were originally intended to stand on large plots of land around a public square. While Bulfinch wasn't able to focus solely on mansions—the prevailing architecture of the neighborhood includes rowhouses and pairs of houses that are symmetrical in design—a few of these historic Beacon Hill mansions are still standing, and one of them is 40 Beacon Street

40 Beacon Street is on the market as a current single-family home. One of Boston's largest and oldest Beacon Hill mansions, 40 Beacon Street includes 13 bedrooms and 13 bathrooms in its more than 20,000 square feet of space.

The existing configuration of this home features three separate areas as designed by famed Boston architect Alexander Parris. First is a main house that has a grand access off of Beacon Street, a living room, a master bedroom plus six guest bedrooms, a sitting room overlooking Boston Common and a 1,300-square-foot roof deck.

"The Link" is next, and encompasses the kitchen, family room, two bedrooms and a garden terrace. The first floor of this area even includes a "turn-of-the-century ballroom" with a service kitchen and elevators to the floors above.

After that comes the "Carriage House," which you enter through a gated driveway. Here, you'll find four more bedrooms, a dance studio, home gym, three-car garage, wine cellar and storage all in five floors of space. 

The expansive home is on the market for $20 million. Though it is set up as a single-family home now, it can possible be sold as four or five units. Proposed redevelopments to turn this one mansion into a multi-unit building can be seen here and would include expanding the home with 1,844 additional square feet as well as adding underground parking for nine vehicles in the existing basement. 

For more on this listing contact Colliers International at (617-330-8013).