At the outset, the venerable old brownstone was perhaps more whoa than wow for Bella Mancini. “To be honest, I was a little bit terrified when I first saw it,” admits the designer of the 1890s building her client envisioned transforming into a modern family home. The four-story, once-grand private residence had suffered many affronts during the years it had been sliced and diced into a “single room occupancy” maze. Her client could see her initial reaction. “After our first tour, she said ‘I hope you’re not scared off,’” Mancini recalls.

That fear, however, was soon assuaged by the building’s residual fabulousness. For the clients, as well as for Mancini and architect Scott Hirshson, the brownstone’s original elegance—from mahogany paneling in the foyer to an intact staircase to beautiful plaster cove moldings and fireplaces—shone through the scars from modifications over the years. That, plus ample space to accommodate a growing family, had been the selling point for the homeowners, who felt constrained in their Upper West Side apartment.

“After our second baby, we realized we needed more room. My husband and I both grew up in houses. We wanted space for kids to be able to play and to have people over without having to shove toys away in a closet,” says the wife. Not until happening upon a listing for a townhouse at their price point, she adds, “had it ever really occurred to me that you could have a house in Manhattan.” When their realtor sang the praises of Harlem’s hidden gems and neighborliness, the couple extended their search north and found the historic building in a landmarked district. “The bones were still there and still elegant,” the wife says—but it needed serious TLC.

Hirshson embraced the challenge of restoring the home’s original grandeur, while making prolific adjustments—for example, adding a large kitchen and breakfast room on the garden level, and digging out a basement to accommodate a workshop for dad and Lego-heaven for the boys. “We first thought about how the home was originally intended to be used, then translated that into a more modern sensibility,” says the architect. “It was truly a gut renovation, with restoration.” Working with general contractor John Hite, the team removed and catalogued trim, doors, paneling and fireplace mantels, and refurbished what they could, often repurposing it elsewhere in the house, such as the mantel in the primary bedroom, which was salvaged from a guest room and freshly stained.

To address light and flow challenges innate to vertical townhouse living, Hirshson added a skylight at the rooftop stairwell, cascading light throughout the floors below, and enhanced aesthetics and functionality, like his repositioning of the primary bathroom to gain a window—“a real luxury in New York,” he says. “In no moment does this house feel narrow and dark, and that’s because the design was so purposeful. There are a lot of character moments,” adds the architect, noting a touch of nostalgia via a window he incorporated into the third-floor landing, which was salvaged from the college dorm where the clients first met.

There are plenty of vivid colors and lively patterns, too, thanks to Mancini and lead designer Taryn Burns’ exuberant choices. “I love that the client favored such strong, saturated colors—there’s nothing muted. The palette complements those rich, bold woods so nicely, and the house’s grandness allowed us to be playful with the design,” says Mancini. To wit: koi swimming along blue dining room walls, jellyfish gracing the powder room on the parlor-level (the “fancy floor,” per the wife), and a splash of custom tile in delicious apricot and blue framing the garden-level breakfast nook. Even in the entryway, Mancini amped up the fun with a mosaic-like wallcovering and a graphic light fixture, which are visible from the street. “I love the idea of entering into a jewel box. It says immediately that you’re in for a treat,” she notes.

For the homeowners, the real treat also extends beyond the front door. The family loves being in close proximity to Central, Morningside and Marcus Garvey parks, as well as to great neighborhood restaurants—and great neighbors. “Harlem’s stoop culture is real!” shares the wife. “We have cocktails and dinners outside on the stoop. For the first time since living in New York City, we have friends on our street.”