Antwerp, South Korea

A block from Dosandaero, a bustling thoroughfare in the Gangnam district of Seoul, South Korea, a garden appears to grow upward. Sprouting over the facade of a three-story building, the lush greenery serves as a prologue to Ann Demeulemeester's urban men's and women's clothing—a mix of rock, punk, and military styles favored by the likes of musician Patti Smith. Demeulemeester is one of the Antwerp Six, credited with putting the city on the fashion map in the 1980's after they graduated from Belgium's Royal Academy of Fine Arts. Noted for her experimentation with fabric and form, Demeulemeester unhesitatingly gave the go-ahead to architecture firm Mass Studies when principal Minsuk Cho suggested cloaking her shop in a herbaceous perennial.

In densely populated Seoul—the world's second biggest city, with 23 million inhabitants—the vertical foliage is especially "compelling," as Cho puts it. Plus, Mass Studies has an obsessive-compulsive need to include greenery in architectural and interiors projects. (The firm's nearby office building has a green roof, too.) Although literally green, the building shared by Demeulemeester and two other tenants is not billed as sustainable. "There are, in fact, ecological benefits, such as insulation and cooling," Cho continues. "But the main question for us was: How do we engage the public?"

He was starting from scratch, with a tight 60-by-66-foot empty lot where a 1970's house used to stand. Demeulemeester's Korean partner, Handsome Corp., had selected the spot for its prime location in a residential area transforming into a destination for high-end fashion boutiques and trendy cafés. Although the building would be mixed-use, with revenue-generating tenants above and below the Demeulemeester boutique on the ground level, the overall design of the 7,900-square-foot structure would reflect her brand identity.

After studying photographs of her hometown shop and visiting her Tokyo outpost, Cho proposed a concrete shell with curved window walls, a deconstructed interpretation of the tall arched windows found at her 19th-century Antwerp building. He notes that his living facade of pachysandra, planted in 16-inch squares, is the "genetic offspring" of the traditional garden at the Antwerp store. Already, there's a miniature ecosystem flourishing amid the pachysandra leaves. Other small plants have cropped up, and Cho expects future happy residents to include a lizard, frog, or two.

The leaves cover not only the building's boxy main volume but also an L-shape extension that embraces a cobblestone parking lot and houses staircases up to an Indian restaurant on the two top levels and down to a separate clothing boutique in the basement. The journey to the basement is like entering a subterranean cave, deep in the forest. Limestone steps descend beneath an elongated skylight, past moss-lined walls watered by mist sprayers. Purified and oxygenated by the moss, the air is unexpectedly cool and fresh.

With the staircases discreetly handling tenant traffic, Demeulemeester's shop is clearly the building's centerpiece. The 2,000-square-foot interior follows the international brand guidelines established by Demeulemeester and her photographer husband, Patrick Robyn: Flooring is dark-stained oak; walls and display cases are white. In a departure from the label's minimalist identity, the biomorphic ceiling undulates overhead in earth-tone cast concrete—a structural feat that required beams to be installed in an unusual sideways W formation as opposed to the typical grid. (To accommodate a 3-foot difference in ceiling height, the floor of the restaurant above steps upward at the front.)

Partitions are white canvas stretched over wooden frames, as if in preparation for an oil painting. One partition runs right inside the front window, partially screening the boutique from the street. Because the building's other three sides stand only 3 feet from neighbors, Cho planted rows of bamboo in between, creating the illusion of openness. "It's as if you're dressing in a garden," he says. "When Ann walked in for the first time, she said she felt at home." That's a particularly gratifying compliment from someone who happens to live in a house by Le Corbusier.

Previous spread, left: The herbaceous perennial pachysandra clads Mass Studies's three-story mixed-use building in Seoul, South Korea. The ground level houses Ann Demeulemeester's 2,000-square-foot boutique.

Previous spread, right: Walls cloaked in irrigated moss flank the Italian limestone steps to the basement, which is occupied by a separate clothing boutique.

Opposite top, from left: Identical limestone steps, minus the moss, lead to the Indian restaurant on the two top levels. The restaurant's front window runs across the full 36-foot width of the building's main volume.

Left: Lacquered display cases in the Demeulemeester boutique are identical to the ones at her shops worldwide. Right: As the basement stair descends, it widens from 12 to 32 feet.

Top: Incandescent lights on a steel track ring the boutique's ceiling of cast concrete, tinted with iron oxide. Bottom, from left: Steps in the restaurant's concrete floor accommodate the upward swoop of the boutique's ceiling. Demeulemeester's clothing hangs on steel racks set against partitions of cotton canvas stretched over wooden frames.

Opposite: The curtains of fitting rooms at the Demeulemeester boutique are visible from the parking lot.

Left: Housed in a volume to one side, the stairs up and down benefit from a curved window and a skylight. Right: Steel wire holds the 16-inch squares of pachysandra in place. The plants are rooted in a layer of crushed bamboo and watered by concealed rubber hoses perforated to drip continuously.

Opposite bottom, left: Flooring in the boutique is stained oak. Opposite bottom, right: The main entry is part of the 15-foot-high front window.

BUMHYUN CHUN; WONBANG KIM; JIEUN LEE; JOONHEE LEE; ZONGXOO U; HYUNSOO YEO: MASS STUDIES. TEO STRUCTURES: STRUCTURAL ENGINEER. CG ENGINEERING& CONSULTING CO.: CIVIL ENGINEER. HANA CONSULTING ENGINEERS CO.: MEP. GEOMANG DESIGN: GENERAL CONTRACTOR. PRODUCT SOURCES FROM FRONT GARDEN IN FOREST: PLANTS (EXTERIOR). HAPDONG STEEL: FRAMING. AURA: PAVERS (PARKING). VIVARIA CO.: MOSS (STAIRWELL).