The elegant five-story brownstone at 51 Appleton St. currently comprises two units. The lower triplex has three bedrooms and two bathrooms; the upper duplex has two bedrooms and one- and-a-half bathrooms.

Nestled in the heart of the South End’s Golden Triangle, this two-family building (on the sunny side of Appleton Street) has several unique features. One: this is a “free-standing” multi-unit building and not a condominium. In other words, no monthly fees.

Two: the property can be easily converted into a single-family home and, three, Joe Baglio of Back Bay Residential has listed this 2,900-square-foot townhouse with five bedrooms, three-and-one-half bathrooms for $3,175,000.

The elegant five-story townhouse at 51 Appleton St. currently comprises two units. The lower triplex has three bedrooms and two bathrooms; the upper duplex has two bedrooms and one- and-a-half bathrooms.

The nine-foot-high (plus a little extra) ceiling with recessed lighting and triple crowned moldings with picture rail trim accentuates the oversized windows in the sizable parlor-level living room. Wide dark-stained pine floorboards are beautiful as stand-alone features throughout the residence. They also make a dramatic backdrop and add a cohesive element.

A beautiful marble-arched wood-burning fireplace with a classic mantel is an attractive focal point in the living room. This room, which can accommodate dining space (formal or otherwise), is fully open to a stunning kitchen.

With its clean-lined white cabinetry accented with black granite countertops and stainless-steel appliances (a Sub-Zero refrigerator, Bosch dishwasher and five-burner Viking range with Broan range hood), the wide galley kitchen reflects a contemporary aesthetic. The room is large enough for a table that seats six or a large center island that can double as a server when entertaining - be it casual or formal.

An eight-foot-six glass paned door opens to a private deck that overlooks the fully enclosed garden patio.

“Large” is the norm for two bedrooms on the next level. One has a custom floor-to-ceiling double closet and a built-in bookcase.

The other room that easily handles a king-size bed also has ample closet space. The bathroom does a contemporary take on period styling. The pedestal sink sits on chrome legs and has chrome “bars” for towels. Oversized tiles on the floor are another modern statement. The tub/shower combination has tile surround.

A private bedroom on another level has character to spare. This very large room (think king-size bed) has a wide display ledge on three walls and walkout access to the patio.

A full bathroom contains a step-in shower with a frameless glass door. A sweet wall-mounted sink is a charming touch.

Convenience is the essence of a large in-home laundry room, complete with a full-size Miele washer and dryer, a sink and shelves.

The upper duplex has a reverse floor plan. While the first level accommodates the sleeping quarters, the open concept living area occupies the second floor with access to a full staircase to a private roof deck with stunning 360-degree views of the city.

Each of the two bedrooms is generously large, albeit one is a tad bigger with a built-in seven-shelf bookcase. Both rooms are filled with natural light. One bedroom has three windows, the other has two, and all are extra-wide two-over-two panes.

Double crown molding, detailed bump boards and ample closet space are also the norm. One bedroom has an extra-wide double closet with open shelving and the other has two large single closets with closed overhead cabinets.

The shared bathroom has a tub/shower combination with tile surround.

In the spacious living room, a striking marble front wood-burning fireplace is a dramatic contrast to dark-stained wide pine floorboards that flow throughout the unit. Rooftop views via four two-over-two windows above a wide ledge create an atelier ambiance in this well-proportioned room.

A nearby half bathroom has a pedestal sink.

The open kitchen-dining room has a decidedly sophisticated “country” look. White cabinetry is a pleasing contrast to honed black granite countertops in the long galley kitchen that includes a gas range with a stainless-steel hood. This large space has ample room for a freestanding center island plus a dining area comfortable for at least six or more.

A long built-in window bench is a charming touch. The oversized skylight is unexpected yet practical. The rooftop window lets in natural light.

Laundry facilities include a full-size stackable washer and dryer.

The building offers more than just being pretty, however, as the structure has recently undergone substantial renovations that include a new roof, copper gutters and all new custom Marvin windows with a transferrable warranty.

The new roof deck has a new railing and a spring-latch Plexiglas roof hatch. While the brick has been repointed, the fully enclosed (it’s a new cedar fence) patio has been re-graded, ready for brick or bluestone pavers. The house is wired for sound and has air conditioning.

Despite the name, the South End does not sit directly south of the center of downtown Boston, but lies south of the Back Bay, adjacent to Roxbury, Dorchester and Bay Village, and should never be mistaken for its southeast counterpart, South Boston, another fine neighborhood in its own right.

According to Wikipedia and the South End Historical Society, the South End is the largest intact Victorian row house district in the country. The tree-lined streets graced by connected red brick bow-front townhouses with limestone or granite trim surrounded by cast iron gates and railings provide striking visual unity. In 1973, the South End was listed in the National Register of Historic Places.

Once a strip of land surrounded by tidal/salt marshes, today the South End has more than 300 acres of land showcasing residential parks and community gardens – many with beautiful fountains – scattered around the neighborhood speckled with numerous restaurants, shops, galleries and entertainment arenas.

Since the 1880s, the South End has been characterized by its rich multi-cultural, socio-economic diversity. Until the 1950s, the South End was a jazz mecca. As the jazz era waned, Wally’s Paradise or Wally’s Café as it is known today, survived, broadening its musical genres for many to enjoy. Wink & Nod, established in 2014, embodies the good spirit of yesteryear’s speakeasy with modern flair, where visiting chefs come to experiment and showcase their boldest creations. The South End is also home to the SoWa (South of Washington Street) Art & Design District, a vibrant world-renowned award-winning retail and arts community, sharing their products, purpose and passion.

There will be an open house at 51 Appleton St., South End, Boston from noon to 1:30 p.m. on Sunday, May 6.