High art attraction: at the top of a skyscraper, this new art museum rises above the blare and distraction of Tokyo.

The upper floors of a ritzy skyscraper may seem an unlikely home for a museum of contemporary art, but in the metropolitan context of Tokyo almost anything is possible. The Mori Art Museum occupies the top of a 53-storey tower designed by American practice Kohn Pedersen Fox, the tallest constituent in an eclectic assemblage of projects (with contributions from Fumihiko Maki, Conran & Partners, and LA's Jerde Partnership) collectively branded Roppongi Hills. The museum is thus literally the jewel in the crown of this multi-billion dollar development that, if somewhat unreal or kitsch at ground level, is spectacular and singular several hundred metres above the Tokyo streetscape.

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Two elements--the museum interior up in the clouds and a bulbous pavilion down at street level--are the work of Gluckman Mayner Architects of New York. Richard Gluckman has been at the forefront of gallery design for at least a decade, rehabilitating many post-industrial spaces (including New York's DIA Center for the Arts and the Andy Warhol Museum in Pittsburgh) with an attitude to materials and to the coexistence of old and new that is both minimal and sensory. In Tokyo, visitors to Roppongi Hills are enticed into the principal tower by the pavilion that is part formal folly, part technical gizmo but nevertheless a cool, tasteful element in this highly saturated design environment.

The pavilion's central structure is a concrete cylinder that curves out towards its upper rim like a giant mushroom or inverted funnel. Containing a set of lifts that connect three levels of expensive-looking boutiques, the circular shaft is also entwined by cleanly detailed spiral stairs. Fitted from the rim of the concrete canopy is a delicate frame of horizontal rings held in situ by a diagonal net of stainless-steel cables.

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Swelling outwards and overlapping each other, rectangular panes of glass are attached to this frame such that the pavilion is like a slightly bulbous truncated cone that is not entirely sealed but glows seductively, in winter or at night-time, as a building-size chandelier.

Roppongi Hills is the most prestigious project yet by Tokyo's omnipresent Mori property company (artist Mariko Mori is niece of the current patriarch). Visitors to the Art Museum cross from the pavilion to the tower's lower foyer via a glazed footbridge; then ascend to the 52nd floor in a bank of dedicated lifts shared with visitors to Tokyo City View, an observation deck protected from the elements by floor-to-ceiling glass. Together, the museum--perhaps more accurately described as a ring of galleries for changing exhibitions--and the double-height viewing deck create a hybrid attraction, the former encircled by the latter but occasionally protruding into its space and stealing breathtaking glimpses of the city's rooftops.

Spaces dedicated to art, however, and an internal, orientation hall are essentially introverted. Visitors arrive into this latter volume, a cube lined in sandstone and fitted with an elliptical deck trimmed by a balustrade of yellow glass. They then rise on escalators up through one eroded corner to find themselves in the panoramic gallery looking out over Tokyo and proceed in a circular pattern. The casual tourist may be surprised to pass beneath the mirrored soffits of two special galleries thrusting out from the upper level and reflecting--upside down--streets and the rooftops of houses close to the base of the tower.

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The lower of the two museum levels mixes gallery functions with those of Tokyo City View and such inevitable tourist facilities as a cafe and bookshop. Visitors purchase admission tickets in this outer zone before re-entering the hollow core of the tower and rising to the 53rd storey. With lavatories and staircases embedded in the thick, opaque layer about this upper atrium, gallery spaces are arranged in box-like enfilade with a few, key skylights to admit natural light and occasional--if dramatic--glimpses to the exterior. Two of these moments occur at the projecting Art and Technology Galleries (Gluckman originally thought these might pierce the tower's outer membrane). Another is offered about an internal, open staircase wrapped in yellow glass that curves about a small, secreted cloakroom.

Observant visitors will notice an elliptical theme both in the footprint of the Kohn Pedersen Fox tower and such Gluckman Mayner insertions as the internal escalator lobby and panoramic stairs. A characteristic refinement is evident here in the maple floors, white gypsum walls, meticulously installed cement board, and ceilings with their unobtrusive, recessed lighting fixtures. However, such hot colours as the chartreuse balustrade upstairs or the bright cherry glass walls to members' rooms below, on the 51st floor, suggest that Gluckman Mayner felt that here, in hyper-capitalist Tokyo, more was needed than discretion. Inside the corporate tower, a more sensory or emotional architecture is poised to break out.

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