Hamburger stakes.

What started life as a mid nineteenth-century railway station has in its latest incarnation been transformed with a rigorous Rationalist approach into an art gallery.

Josef Paul Kleihues's contribution to the reconstruction of Berlin, which began in 1979 with his direction of the Neubau section of the massive urban programme of the International Building Exhibition (IBA), is still significant (AR special issues September 1984 and April 1987). His recognition of the importance of history, of 'critical reconstruction', valued the traditions of the city block and urban space. The vast range of residential and other projects constructed for the IBA are a testament to his wisdom, which challenged the tabula rasa policy of the '50s and '60s, and reclaimed city space for daily life.

His preoccupation with the work and lineage of von Klenze and Schinkel, Behrens and Mies, together with the Modernist masters of the 'roaring '20s',(1) is paralleled by post-graduate experiences with the Academie des Beaux Arts in Paris and exposure to typological Rationalism, systems of proportion and modular grids, coupled with technology as a form-giving process. Kleihues's reference to his work as 'poetic Rationalism' is therefore rooted in this background of French Rationalism, as much as it is naturally embedded in the historical figures of German architecture from the Enlightenment to the age of Mies.

From this position, Kleihues emerged as the natural architect for the Hamburger Bahnhof,(2) selected in a restricted competition announced in 1989. The Hamburger Bahnhof: built in 1845-47 as terminus of the Hamburg to Berlin railway, is sited in Invalidenstrasse, Berlin. The original buildings, a combination of late Neo-Classical masonry with the iron skeleton of the platform hall, were closed in 1884. Between 1904 and 1906, the station was converted into a transport and engineering museum. In 1914-15 two additional wings were added to the major portal frontage, enclosing the former railway turntable, and transforming it to a kind of cour d'honneur, which is the entrance focus of the new project.

The buildings were severely damaged in the Second World War and subsequently fell into disuse. Ultimately, following a series of trial exhibitions in 1987, it was decided to restore the place for use as a museum of contemporary art. The building's history forms the basis for Kleihues's approach, of which he says 'The first aspect of the cultural intentions concerns appropriate (not nostalgic, but Rational) analysis of the historic building substance of the Hamburger Bahnhof and memories of its architectural and historical significance, Being prepared to remember this must not be related only to what was, but has to include what could be or should be. Casually speaking the memory concept is just as much related to the relationship of reason and history as with the premise of reason as freedom. Thus in the present design, securing the existing building has been discussed with the regional (authority) responsible for preservation of historical monuments in some detail. Beyond this, great value was laid on the aura of "Hamburger Bahnhof identity" conveyed by the architectural geometry. An attempt has been made by extending the former station and adding additional buildings to establish a dialogue between tradition and modernism. What in the best sense the architecture of the Enlightenment and humanism always was in Berlin turns out to be a "memory that secures existing building stock", first and foremost in the geometry of the historical building ensemble and the new buildings that have been added. This refers to their ground plan, their spatial order and the geometry of their individual sections.'(3)

In the conversion of the buildings Kleihues has adopted two distinct strategies. First, he cleared away the masonry buildings which once lined the Platform Hall (now called the Historical Hall) and replaced them with two elongated barrel-vaulted galleries on the east and west flanks. These spaces are united by the restored Central Hall with its iron and steel structure finished in grey metallic paint with off-white stucco infill. Next, the remainder of the masonry parts have been stripped and reformatted internally with a rationalised structural pattern of beams and columns, finished throughout in off-white piaster, with Striegauer granite floors at ground level in the public spaces, and existing tiles retained wherever possible.

Doors are lofty, openings are severely vertical and the detailing throughout follows a strict, acutely minimal format. The conservation of the original fabric retains all its essential historical features. Externally the existing ashlar Neo-Classical masonry forms have been finished throughout in cream masonry paint, which unifies the various parts. The cour d'honneur has received a grey granite podium which emphasises the raised piano nobile of the entrance portals, standing between the city-gate formed by the twin towers of the former railway station. The linking gallery over the entrance is the one highlighted element, in yellow which, illuminated at night, acts as a spectacular marker. The overall impression is of extreme austerity, with the focus on the entrance portal space, the Historical Hall and the barrel-vaulted East Gallery, with the West Gallery waiting to be added as a future identical stage.

The Historical Hall, with its faintly Art Nouveau structure, has received minimum interference. Symmetrical staircases, and the bridge over the entrance portals, are in white square-section steel with cast-glass treads. Otherwise the indented granite paved floor, which 'remembers' the station platform, forms a vast open space with clerestories and top-lit side aisles supplying natural light. A pair of huge pivotal steel and glass doors at the end of the hall prepare for access to a future quadratic piazza which finalises the plan. Kleihues has deliberately held back to reveal the order and rational geometry of the late Neo-Classical and engineering structures.

Only in the East (and future West) gallery spaces is the new work allowed to speak both externally and internally. Outside, the grey steel-framed buttress structure with its shipshape columns is infilled with cast aluminium panels or glass at the junctions with the Historical Hall. This tectonic skeletal mass is contained within a grey Krailsheim shell limestone plinth and gables, capped with a continuous glass roof which supplies natural light or artificial light as required. Within, the space is extremely simple in its finish with seamless floors, laid with 1.2m oak planks, white walls and glass barrel-vaulted ceiling.

But it is the plan and section that are most significant. The plan of the volume is separated from the central Historical Hall by a deep service zone. The section itself is based on a 10.8m square into which a circle is inscribed and revealed in the barrel-vaulted section. This Vitruvian device and the circular geometry have other relationships - to the similar geometry of the entrance portals, and it has been suggested,(4) to the idea of the wheel and the turntable that are part of the 'Hamburger Bahnhof identity'. More important still is the new architecture which incorporates the tectonic order of an engineering structure to enclose a gallery space, the awesome length and section of which echo both the Neo-Classical origins of the project, and Kleihues's predilection for French Rationalism of the age of Boullee.

As a building in the service of contemporary art, the project is an unqualified success. The simple white interiors of the gallery rooms on all three levels provide a neutral setting for both installations, paintings and sculpture alike. Galleries are generally side-lit by windows which can be screened with simple manual blinds. Artificial lighting is either linear and contained within the ceiling structure zone, or in a universal gridded glass soffit. Otherwise, the Historical Hall which can house huge exhibits - such as a Richard Long stone-circle - has variable top and side-light and the barrel-vaulted East Gallery with its unbroken walls provides a magnificent setting for paintings which can be either naturally lit from the continuous skylight, controlled by louvres above the barrel vault, or alternatively artificially lit from the same source.

The building is at once very much a Berlin piece, driven by the intrinsic minimalism of Kleihues's 'poetic Rationalism', at the same time it is an art-event - it functions, it attracts and is already a thronged landmark in the city.

1 From a recent discussion with the author in Berlin.

2 The architectural structure of the passenger railway station was built 1845-47 by the engineer Frederick Neuhaus and the architect Ferdinand Wilhelm Holz for the private Berlin-Hamburg railway company. In 1884 the railways were nationalised and the subsequent use of the Bahnhof as an educational museum of transport and building, established in 1906, related directly to the development of railway technology and was used to train railway employees. This stage of the building's re-use was opened by Kaiser Wilhelm II, as a state facility.

3 Kambartel, Walter, 'Between the Winged Wheel and Pegasus: Conversion of the Hamburg railway station in Berlin into the Museum of Contemporary Art' in Mesecke, Andrea and Thorsten Scheer Josef Paul Kleihues: Themes and Projects, Birkhauser Verlag, Basel, 1996, pp220, 221.

4 Ibid p231.