Ranked second on the 2012 A-List of the American Lawyer, the Los Angeles–based Paul Hastings LLP is a 61-year-old firm with a progressive global vision—one that incorporates good design into a business strategy that aims to attract prime talent and clients with leading-edge facilities. So when the managing partners decided to open a Frankfurt office after a 2008 merger with the German firm Smeets Haas Wolff, they tapped architect Lauren Rottet to regenerate a high-profile 1950s location to reflect the open work style they embrace. Their new address is not only on a leafy residential street in Frankfurt's affluent Westend neighborhood next to the city's gorgeous Palmengarten and Botanical Gardens, it also has an intriguing architectural pedigree.

Siesmayerstrasse 21 is a 1955 building by Gordon Bunshaft of Skidmore, Owings & Merrill that echoes his 23-story Lever House in New York City (1952), both in plan and by virtue of its distinctive facade made of contrasting rows of clear and tinted glass framed by a metal grid. Part of a diplomatic initiative as complex as a James Bond plot, the five-story structure is one of five similar U.S. Consulate buildings in West Germany designed by Bunshaft in collaboration with German architect Otto Apel, an assistant to Albert Speer from 1933 to 1943. The post–World War II era was fraught with Cold War politics, and the State Department commissioned America's top Modernist architects—including Harrison & Abramovitz, Ralph Rapson, and Edward Durell Stone—to design facilities around the world as symbols of democracy, culture, and power. “Architectural modernism became linked with the idea of freedom after the war,” writes Jane C. Loeffler in her fascinating Architecture of Diplomacy (Princeton Architectural Press, 1998). Bunshaft's style, she says, was considered one of the most “American,” and Lever House had the look and quality U.S. officials wanted to export.

Rottet, who has created more than a dozen interiors for Paul Hastings over the past 10 years, says, “The building is a Modern gem, and I recommended that they lease it as soon as they showed it to me.” It fits with the firm's program. Unlike traditional law offices, she explains, Paul Hastings wants to be seen from the street. The building's footprint and glazing allow for that visibility, with a single-story base shaped like a square doughnut, topped by a shallow, recessed mezzanine and three-story office block across its north side.

Prior to the firm's lease, the building changed hands from the State Department to the German developer Gross & Partner, and underwent a structural overhaul led by the Frankfurt-based architects Schneider+Schumacher in 2007. Repaired and reglazed, with a new underground parking garage and freshly landscaped grounds, the 57-year-old landmarked building appears unscathed by the rigors of time and bureaucratic management. Its scale, massing, and reflective qualities provide an elegantly contemporary counterpoint to the surrounding streetscape dotted with turn-of-the-20th-century Wilhelminian-style buildings.

“We definitely wanted to work with the architecture to create an interior that looks like it could have been there forever,” explains Rottet. Ironically, budget constraints curbed Bunshaft's original vision for the interior, and records indicate that designer appointments, such as Knoll furniture, were the exception, not the rule. Free of rigid historical criteria, she devised a timeless modern scheme.

In keeping with the building's International Style, Rottet opted for a minimalist palette of materials and furnishings. Because the structure was gutted during the restoration, the architect and her team at the Houston- and Los Angeles–based Rottet Studio were able to retain the openness of the architecture without major demolition. First the HVAC was upgraded with sleek, low-profile radiators beneath the windows and an energy-efficient radiant-cooling system in the ceiling. (Forced air conditioning is used sparingly and vented through subtle ceiling slots in conference rooms and event spaces.) Then they installed terrazzo flooring, noise-resistant transparent or white walls, and fluorescent lighting recessed into perimeter ceiling and wall coves or downlight fixtures, carefully maintaining unobstructed views throughout.

Paul Hastings is the building's anchor tenant, occupying the first three floors and lobby. To remain prominent, the firm's receptionist doubles as host for the businesses on the upper floors as well. For privacy, Rottet tucked a cherry-wood reception desk to the left of the entrance and installed a wall of lacquered panels behind it that slide out on either end to close off the firm's inner space when necessary. Likewise, she concealed an adjacent conference room with glossy, opaque tempered glass. A composed seating area in soft neutrals serves as a tranquil lobby lounge.

The client originally wanted to put offices in the lobby, says Rottet. But it didn't really need the space, and the architect “felt it was important to emphasize the building's transparency.” She convinced the firm that this area would be an ideal focal point to establish the company's presence and for entertaining. Then she organized day-lit banks of glass-enclosed offices, open support stations, a library, and pantries along the north, west, and south halls of the ground floor and on the two upper levels overlooking the courtyard.

Rottet's most surprising and gracious move lies behind the wall backing the reception area, where she created a hybrid entertainment/work lounge dominated by a striking marble bar and generous seating arrangement. It is very discreet: She covered a kitchen and restrooms with low-luster, solid-surface doors and tucked a closet behind pristine, back-painted glass. This luxurious touch of Bond happens to be extremely functional, says the local director of office administration, Elena Ernst. “Clients come here between meetings to make phone calls,” she says. It's a place where they can sit and relax. It is also where the firm hosts parties.

It's hard to believe that this urbane setting was once a haunt for travelers and expats, hidden behind venetian blinds and filled with standard-issue government furniture. Rottet's refined transformation enables this mid-20th-century classic to take on the 21st—identity intact.

Cost: withheld

Completion Date: June 2008

Gross Square Footage: 20,864 sq. ft.