This four-story Federal-style home with three bedrooms and three-and-a-half baths has been meticulously maintained and updated not only to provide modern-day amenities, but also to reflect an understated elegance.

One of the most photographed and picturesque streets in the country is on Beacon Hill, according to Barbara W. Moore and Gail Weesner, authors of “Beacon Hill, A Living Portrait.”

It’s Acorn Street, a narrow road, almost a path, between Willow and West Cedar streets, paved with cobblestones and lined with brick walks and gaslights.

Architect-builder Cornelius Coolidge built the nine brick row houses on Acorn Street between 1828 and 1829, including Number 4, which Tracy Campion of Campion and Company Real Estate has listed at $3,495,000.

This four-story Federal-style home with three bedrooms and three-and-a-half baths has been meticulously maintained and updated not only to provide modern-day amenities, but also to reflect an understated elegance.

Its exterior is quintessential Beacon Hill – a flat façade, six-over-six windows with granite lintels and sills and a recessed entry with sidelights and a multi-paned arched transom.

Four steps – two of granite and two of wood – ascend to the front door, which opens into a striking marble foyer with radiant heat and a soaring ceiling rimmed with crown molding. The home has a side hall plan; on the left, a gracious staircase with curved bottom stairs ascends to the upper floors.

A wide arched doorway opposite the stairs leads into a light-filled formal living room centered by a handsome fireplace, flanked by built-in bookcases, each with an arch. Two six-over-six windows at the back of the room look down onto the patio/deck and the glass atrium in the kitchen ell.

The foyer continues straight ahead, past a coat closet, to a magnificent butler’s pantry/wet bar. The counters are honed dark granite, and custom-designed china cabinets hold stemware. Top-of-the-line appliances include a Sub-Zero wine refrigerator with cooling drawers and a compact Bosch dishwasher, faced with cherry to match the cabinetry. The sink is hammered copper.

More entertaining space is on the garden level where there is a large family room with a big brick fireplace with a white wooden mantel. Bookshelves are on either side of the fireplace, and against an exterior wall is a dining area.

A pair of tall French doors open onto a 140-square-foot patio topped with an ipe deck enclosed by brick walls and latticework. There are gas and irrigation lines for convenience.

An elegant powder room with a pedestal sink is at the base of the stairs, and across from them is a large pantry closet. Beyond the family room is an outstanding kitchen. A wall of windows topped with an atrium floods the galley-like kitchen with natural light and creates a sense of spaciousness.

A Bosch stainless steel French door refrigerator with a bottom freezer stands between the black granite counters. Set in one counter are the four-burner gas cooktop and Bosch range. Opposite is a double sink beneath the windows that look out to the patio. Under the windows is a long black granite shelf that is a perfect spot to sun vine-ripened tomatoes or grow herbs.

The custom-built glossy white cabinets are a nice contrast to the counters. Nearby are stairs to the basement, which offers abundant storage and holds the mechanicals, including a Utico gas-fired furnace.

Above the living room is an extraordinary library, plus two other rooms. The library is paneled with quarter-sawn oak, and the ceiling is covered with gold leaf. (The floor is oak, as are most other floors throughout the house.)

Centered in the room between bookshelves is another fireplace with an oak mantelpiece and a slate surround and hearth. More shelves and a long window seat beneath a multi-paned window are on an adjacent wall.

A home office with a built-in desk and open shelves overlooks Acorn Street; at the far end of the hall is a full bath/laundry room. Mirrored doors conceal the stacked washer/dryer, and another mirrored door and adjacent panel hide the shower. The mirrors reflect the window light and brighten the hand-painted red walls.

The master bedroom boasts two sets of French doors that open onto a Juliet balcony, another fireplace with a wood mantel and brick surround, more bookcases and two closets. It also has a new en suite bath that includes a glass-enclosed shower with a ceramic tile surround, a pedestal sink and a contemporary marble-tiled floor.

Adjacent to the master is a small bedroom, carpeted, with a closet. Presently used as a nursery, this room easily could become a walk-in closet or a second office.

The top floor has an en suite bedroom, too. The room has a large closet, and beyond the adjacent bath is a walk-in closet with built-in drawers and shelves. The bath has a clawfoot tub and a lovely marble-topped vanity. The marble-tiled floor is laid in a basket weave.

Because it is the top floor, the roofline provides angled walls, creating a loft-like sensibility. Skylights above the windows add even more light to the room. Under the eaves is more storage.

This exceptional home with nearly 2,700 square feet of living space is a hidden gem in the heart of Beacon Hill. And while its exterior remains true to its beginnings, its interior spaces have been enhanced with sensitivity to provide a sophisticated lifestyle.