GEHRY'S GEODE.

The new DG Bank headquarters in Berlin forms part of the wider and ongoing reconstruction of Pariser Platz - but its urban sobriety hides a rich inner life, animated by the interplay of light, form and materials.

Immediately behind the Brandenburg Gate lies Pariser Platz (AR January 1999), the great urban piazza that terminates the triumphal axis of Unter den Linden. Before the War, it was the grandest square in Berlin, site of the American and French embassies, the Adlon Hotel, the Akademie der Kunste and blocks of luxurious flats and offices. After the War and the Wall, it was laid waste and became part of Berlin's deadly no-man's land. Since German reunification it has been rebuilt in an attempt to emulate the spirit of its grand urban past, with new embassies, hotels, and office blocks slotted back into the original street pattern. The rules of reconstruction, which stipulate constraints such as eaves heights, proportions and materials (obligatory stone cladding), do not allow much scope for formal experiment. The result is that Pariser Platz's new occupants resemble a collection of rather bland, expensively dressed guests mingling politely at an upmarket cocktail party. The introduction of Frank Gehry into the mi x might in theory be calculated to induce an element of raciness and unpredictability, but he too has been obliged to conform to the dress code. Being Gehry however, he has still managed to spring a few surprises.

The genesis of the project dates back to 1995, when Gehry's competition entry for Berlin's historic Museum Island was under consideration. At that time, the DG Bank invited him and six others to produce a proposal for the bank's new Berlin headquarters. The brief included financial offices, apartments and semi-autonomous conference spaces that could be hired out to corporate clients. Gehry did not prevail in the museum competition, but his design for the DG Bank won unanimous approval.

The site lies on the south side of the square, in the middle of Pariser Platz's evolving urban jigsaw. The rectangular block is hemmed in on its long sides by Behnisch's new Akademie der Kunste and Moore Ruble Yudell's American Embassy, with the short ends overlooking Pariser Platz and Behrenstrasse. The organization of the new building is a logical response to the constraints of site and brief. A necklace of office spaces extends around three sides of the perimeter, enclosing a huge atrium space (of which more later). The residential annexe, which has its own separate entrance, is placed on the fourth side overlooking Behrenstrasse and a site that will eventually house the Memorial to the Murdered Jews of Europe. Flats range in size from studios to larger maisonettes and are separated from the offices by an elliptical void enclosed by a swirling, shimmering glass wall suspended from the roof that cascades down to a pool below. Two glazed lifts glide up and down through the void like air bubbles.

Gehry has clearly taken the Pariser Platz dress code to heart; both bank and apartment facades are models of sobriety and severity. The apartment block is marginally less austere, stepping back as it rises over 10 storeys with faceted bay windows like concertinas animating the wall plane. But the main bank facade overlooking Pariser Platz is an utterly plain, utterly stripped down composition of creamy buff limestone (to match the Brandenburg Gate) and glass. Openings are punched into the stone to create deeply recessed windows that slide back at the touch of a button to reveal terraces enclosed by blade-like glass balustrades. Clad in 4 inch thick stone, the bank facade is almost as shocking in its solid, rationalist monumentality as Gehry's signature sinuousness and its extreme weight and abstraction only serve to show up the flimsiness of the surrounding pastiche. Ironically, in Berlin's traumatized cityscape, such solidity also embodies a reassuring sense of permanence and institutional stability, doubtle ss important concerns for Gehry's banker clients. (The bank guys loved it', he observed, 'although it cost them a lot of money to do it'.)

Sadly, most Berliners will never see beyond this massive stone wall to the real drama and spatial pyrotechnics within. Radically upturning his expressive gestural vocabulary and relocating it to the interior, Gehry has had to pour his design into the cavity of the perimeter block. Here, Californian ad-hocism meets the European masterplan. The inside is scooped out to form an immense atrium - allegedly one of the largest in the world - enclosed by a delicate steel and glass lattice, improbably morphed and warped to form a barrel-vaulted roof canopy that curves in two directions. Within the atrium is a freestanding structure like a giant horse's head rearing and writhing through the space. Encased in a thin skin of stainless steel, this extraordinary object contains a conference chamber. The inner surface is lined with strips of red oak (finely perforated for acoustic reasons), so being inside the chamber is like being cocooned inside a contorted ship's hull. The regimented orthogonality of the exterior extends to the perimeter offices, which are edged by a series of arcades lined with redoak veneer. From these vantage points, the squirming biological specimen of the conference chamber can be fully appreciated.

Beneath the shell of the chamber is a basement level containing a lecture theatre, along with the bank's, cafeteria and a large foyer; these can be combined to create a generous space suitable for banquets and meetings. Another warped glass canopy, smaller cousin to the main roof, encloses these spaces allowing light to percolate down to the lower levels. (During the course of site excavations Albert Speer's bunker was discovered, but no trace of it now remains.)

As with Gehry's other projects, the translation of initial ideas to built form is achieved through a design and construction process that combines sophisticated computer software programs with a craft approach to building. Initial generative sketches, which defy conventional logic and geometry, must be painstakingly interpreted as a precise system of co-ordinates and known structural and material properties. Gehry develops his ideas slowly, from rough drawings through an exhaustive series of handmade models. Using the Catia program to represent complex three-dimensional objects, these crude wood and cardboard mock-ups are scanned into the computer and digitally translated back into working models and drawings. Employed as an instrument of translation rather than generative device, the computer enables the representation and manipulation of that which cannot otherwise be drawn. In this case, unusually, the exterior presented no such challenges, but the glass roofs and conference chamber proved tests of design and manufacturing ingenuity. The triangulated space frame of the roof is made up of solid stainless steel rods that form six pointed stars screwed into nodal connectors. The complex geometry of the roof meant that the rods meet at different angles, so to match them precisely, the nodal connectors were cut from 70mm-thick stainless steel plate by computer-controlled milling machines. The frame is infilled by 1500 triangular glazing panels bedded on neoprene gaskets. The conference chamber is clad in a 2mm skin of brushed stainless steel plates (basic dimensions 2m x 4m) stretched and fashioned by skilled boatbuilders to accommodate the conflation of complex, bulbous forms.

Superficially, this might well appear a conservative building, but clearly it is anything but. In the extreme and startling contrast between its outer and inner life, it resembles some kind of weird rock or geode that, split open, reveals a spectacular mineral formation. It is tempting to see the entire exercise as a metaphor for Berlin - beneath the haughty Prussian exterior lies decadence and debauchery - but after all it is only a bank and the morphological conspicuousness of the conference spaces is perhaps as much to do with commercial viability as being vehicles of architectural imagination. Yet in the decorous context of Pariser Platz, it is definitely one of the more unorthodox and welcome guests.

Architect

Gehry Partners. Santa Monica, USA

Project team

Frank O. Gehry, Randy Jefferson. Craig Webb, Marc Salette, Tensho Takemori, Laurence Tighe, Eva Sobesky, George Metzger, Jim Dayton, John Goldsmith, Jorg Ruegemer, Scott Uriu, Jeff Guga, Michael Jobes, Kirk Blaschke, Nida Chesonis, Tom Cody, Leigh Jerrard, Tadao Shimizu, Rick Smith, Brace Shepard

Associate architect

Planungs AG - Neufert Mittmann Graf

Structural engineers

Ingenieur Buro Muller Marl Schlaich Bergermann & Partner

Services engineer

Brandi Ingenieure

Facade consultant

Planungsburo fur Ingenieurleistungen

Photographs

All photographs by Christian Richters apart from 1 and 5 which are by Waltraud Krase