This place was a filthy dump when we bought it,” says Cathryn Barmon, sipping tea in a knockoff Le Corbusier chair. “I didn’t want to go barefoot until we’d redone the floors. Mark knew it was a good thing, but I thought it was horrible, sad, and depressing. I couldn’t believe we’d put all our hard-earned savings into this.”

Barmon and her husband, Mark Deutsch, are in their mid-30s, and run a graphic and web design business. This apartment in New York City’s West Village was their first real estate investment. Deutsch corroborates: “We felt like we’d been suckered. Cathryn agreed to buy it, but the deal was we had to gut it right away.”

As luck would have it, they hadn’t been suckered. Deutsch and Barmon bought their apartment five years ago for $240,000. The seller, whom Barmon remembers as “a super-fastidious-looking guy dressed all in Gucci,” hadn’t been as fastidious as he looked. “The ‘before’ pictures we have don’t show the dirt as much as I wish,” she adds, going on to describe how the apartment was crumbling and caked in dust, mold, and those creatures that outnumber, outrun, and sometimes outperform Manhattan’s human population. If Deutsch and Barmon had left their space as is, it would nonetheless have doubled in value by now. But they didn’t, and they don’t plan to sell it anytime soon.

Common sense underlay all their decisions in the renovation. “We just put the place together in a cost-effective way,” says Deutsch, who borrowed power tools from the superintendent to install retrofitted IKEA cabinets in the kitchen and living room. All told, their renovation cost about $50,000. “Living in New York, you want your home to feel relaxed and comfortable,” says Barmon, “not dirty and agitated. There’s plenty of opportunity for that outside.”

Before they moved in, they hired a contractor to gut the apartment in one day, scraping up old linoleum in the kitchen and bathroom and tearing down some drywall that had concealed structural columns and beams. “Before it went co-op, this building was a General Electric warehouse,” Deutsch explains. “These columns were covered in dark green paint, so we wrapped them in stripping material and tore it off, but it didn’t strip evenly, so this textured layer was left. We decided to keep it.” The molded-steel columns and beams, circa 1900, are smooth and speckled with layers of old rust and paint.

The effect sets off the spare evenness of most surfaces in the apartment. The 600-square-foot space—which encompasses a galley kitchen, a nook for the bed, a living room, and a bathroom—boasts only one other dappled surface: a fake “terrarium” in a 3-D rectangle of Plexiglas suspended from the ceiling in front of a white wall. The diorama (as Barmon calls it, more accurately) measures six feet long, six inches tall, and six inches deep. Barmon sculpted the verdant hills inside, and designed a suspension system. “I wanted a slice of green,” she relates.

The terrarium, like the renovation itself, also owes its existence to constraints. “The big blank wall was depressing,” Barmon says. “At first we were going to put our desk there, but then the apartment next door came up for sale, and we were lucky enough to get a loan and buy it for an office. Then our dog, Pooh Bear, was getting old and sick, so she had her bed set up by the wall. When she died, there was just a big void.”

After Pooh Bear died, Deutsch and Barmon went on a trip to Japan, where they saw many of what Deutsch calls “controlled slivers of nature.” Like New York, a metropolis they both adore, Japanese cities can be stifling in their density. “But then you’re looking into a busy, merchandise-packed storefront, and all of a sudden you notice there’s a little planted area behind, a breath of oxygen,” Barmon says. She remembers seeing a tidy countryside of pruned trees, rocks, and moss outside train windows. “I like the combination of nature and sculpture.”

The diorama suspends in a delicate balance between functional object and art form. Barmon stayed away from the kitschy “plasticky-looking shrubs and trees” that sometimes fill mini-landscapes, and opted to include only rocks and moss; the result looks almost real. Providing a “slice of green” without requiring any maintenance, the diorama is highly functional, but its nature-inspired enigma also hearkens to mushroom dioramas by artist Roxy Paine.

With its artful practicality, the diorama seems to epitomize Deutsch and Barmon’s design approach. At the same time, it makes the place unique. “I made it for our pleasure,” Barmon says, “but then we found out everybody who visits loves it, and Mark was like, ‘You have to keep doing this.’ Dioramas aren’t too sophisticated or particular, and you don’t have to be artsy. Kids, elderly people, everyone can appreciate them.” Barmon might be on the brink of a career change; she already has a commission for another diorama, which will soon adorn the office of luxury travel agency Artisans of Leisure, who likely plan escapes for stifled New Yorkers craving more slices of green.