It began as a jagged scribble on a page of lined notepaper. The scribble morphed into a sombre artwork in dark acrylic paint. And that, in turn, spawned hundreds of pages of computer-generated images in a small architectural practice in London. This weekend, Rome will feel the seismic shock of that scribble, whose sinuous re-expression in 51,000 tons of concrete and steel has given the city its Bilbao moment. Zaha Hadid's €150m Maxxi museum of contemporary art is up, and stunning.
But for three hours or so on Thursday, the bow-wave of expectation created by Hadid's presence upstaged the building. It's what she does. After giving a press conference in front of 300 international journalists and Rome's most elegant culture vultures, Hadid was surrounded for 90 minutes by an amoebic shoal of cameramen and interviewers, two personal assistants trailing her like pilot fish. The world's most glamorous architect finally took refuge on a translucent plastic Louis Ghost chair at a table screened from public view behind an angular wall in the huge, triple-height volume of the building's reception area.
Here, tended by her minders, Hadid ranged from subject to subject in the languidly playful way that has become characteristic: the dreadful cappuccino she'd just been served; the appalling outbreaks of intellectual masturbation at London's Architectural Association, where her drawings as a student in the 1970s caused a sensation; the repellent nature of smoked mozzarella; and the fact that her co-principal and chief proselytiser, Patrik Schumacher, simply wasn't eating enough potatoes. Most significant was the way she returned several times to recollections of the original scribbles that ultimately created the wall behind her, and the 100m-long galleries that lay, in skews and curves and giant shelves above her: "I remember every line of those drawings."
Maxxi is Hadid's fourth completed large-scale building, but it is far more significant than the 2003 Rosenthal Center for Contemporary Art in Cincinnati, the BMW factory near Leipzig and the Phaeno science centre in Wolfsburg, Germany. And Maxxi is not an architectural progression, but the very Ground Zero of her work. When she designed the museum, her studio was small, and struggling to get significant commissions. Her breakthrough triumph in the Maxxi design competition turned her from a largely occult architectural legend into a very public one.
Today, Hadid employs more than 300 designers in a converted 19th-century school in Clerkenwell; dozens of blue-chip projects, ranging from opera houses in China to furniture, flicker across the rows of computer screens. And in this delayed revelation of her original big idea for Maxxi, Hadid's wait precisely mirrors Frank Gehry's experience: his design for the Bilbao Guggenheim museum actually began life in his earlier, but postponed, architectural concept for the Walt Disney Symphony Hall in Los Angeles.
Maxxi is the well spring, the scribbled DNA that has informed Hadid's later work. There's a clear architectural link between the geometry of the BMW factory and Maxxi. In the former, part-assembled cars pass on tracks over diners in the canteen; in the latter, when it officially opens in May, artworks will hang from the concrete and fibreglass ribs whose striations form the top-lit ceilings.
But what's this ferroconcrete DNA like? Does it make any sense – or is Maxxi just another grandiose architectural icon for the hard of understanding, or those who crave another pseudo-visionary wow-moment? The first thing to say is that Maxxi makes a much more complex and challenging physical statement than the BMW building, or Phaeno.
The sweeping geometry of its form and its internal configuration are almost baroque in the way they modulate volume, light and glimpsed views. Exterior spaces are intertwined, sometimes dramatically, at other times with an almost graceful restraint. Inside, the drama is much more visceral. Heavy black staircases, underlit by white lightboxes, rise as if in flowing oriental brush strokes into the overlapping volumes of the gallery spaces. We seem to be in an Expressionist film set.
Hadid's metaphors are very different. "The walls of the Maxxi create major streams and minor streams," she says. "The major streams are the galleries and the minor streams are the connections and the bridges." And in reaction to the mixture of an orthogonal urban grid and a diagonal street meeting one edge of the building's site, the architecture mutates into a form characterised by "bundling and twisting".
That phrase is applied to every building designed by Hadid and Schumacher. So, too, are other conceptual mantras that describe the architecture of Maxxi as "porous, immersive, a field space, the notion of drift". The idea of architecture whose masses and spaces drift, says Hadid, has been alien to architecture but is well understood in art. "We take this opportunity to confront the material and conceptual dissonance evoked by art since the 1960s." That path, she argues, leads away from the sanctified object towards "fields of multiple associations and the necessity for change".
And that's a bombshell of a remark because the creative bedrock of Hadid's architecture lies in the avant-garde geometry of Russian Suprematist and Constructivist art in the 1920s; an art whose response to modernity delivered simultaneous jolts of velocity and points of fracture. It was anti-object. But in buildings such as Phaeno, the sense of a sanctified architectural object, something heavy and locked in a specific moment rather than an expanding one, remained. The fact that Hadid is now equating her architecture with the dissonances of 1960s art means that phrases such as "bundling and twisting" may soon be superseded by ideas from new sources – and by different kinds of architectural form.
The weird thing about Maxxi is the way it so vividly relates to her early student drawings, yet also demonstrates a move away from them. The architecture is another kind of art entirely, and the first of Hadid's works to react to the restrictions and promptings of its site with a deference that has not been seen in the past. The roof of Maxxi is one storey lower than the blocks of flats around the site, and the pale concrete has a soft appearance that almost matches the stucco of the 19th-century ex-barracks buildings on one side. The way Maxxi's façades are modelled and the way the bundles and twists of the form have been teased apart have turned a massive form into artfully arranged splays of ferroconcrete tagliatelle.
Only time will tell us if Maxxi works as an art museum and incubator for new artists and architects – a 21st-century Bauhaus in the Via Guido Reni, a quiet street named after the 17th-century painter whose works John Ruskin described as "taint and stain, and jarring discord, marked sensuality and impurity". One can't help wondering what Ruskin would have made of the scribbles, and the concrete, that have finally put Rome in the art world's premier division.