The Barcelona Pavilion made architecture out of reduction - of almost nothingness and vanishing. A new and opposite way from 19th century architecture, which was full of stuff. And that stuff was all about history and meaning. Modernism proposed an escape from history through abstraction - or the evaporation of meaning and narrative from architecture. The Barcelona Pavilion doesn't tell a story; rather it is intended to be an experience of material and space.

Mies' Chicago was something new, something that had only been dreamt have in pre-war Europe. Mies found himself in enormous, simple, innocent America. The cranks, and nooks and soon-to-become ruins of 19th century European cities a long steamer ride away. Europe: organic, dirty, old, riddled with History, and plunging into catastrophe.

Four years before Mies arrived in Chicago, Americas Most Wanted Man was gunned down in an alleyway after leaving a movie theatre with a woman on each arm. John Dillinger was the dashing heartthrob of Chicago's gangland. Dillinger optimised the glamorous and chaotic romance of jailbreaking, heist pulling, on-the-run city of rooks nests, alleyways, and safe houses, of Al Capone, of no-go zones and J Edgar Hoovers nascent FBI G Men. His death marked the decline of Chicago's gangster culture which had grown up around Prohibition, supplying the liquor that the government had tried to ban, but the citizens just couldn't live without.

Hoovers dogged pursuit of Dillinger and gangsterism was a victory of a certain kind of urbanism. One that is reflected in Mies' Chicago projects. Mies is on the side of Hoovers bureaucracy, rather than the ad hoc opportunism of the gangsters. But there is mysteriousness and an impenetrability to his architecture too, just as Hoovers bureaucracy of power was, deep down, dark and paranoid. Mies made bureaucracy into a form of poetry, monumentalising though precision and a ruthless editing of architectural possibility.

In Robert Anton Wilsons 'Illuminatus Trilogy' - a sprawling hippy/counterculture/conspiracy epic, John Dillinger becomes a kind of super spiritual guru of the forces of chaos. His break outs from captivity are retold as a supernatural victory over matter. Dillinger dematerialises the prison walls by the power of concentrated thought - a little like the attempt to raise the Pentagon building by the Chicago led yippies and zippies. The Illuminatus Trillogies retroactive dramatisation of jailbreaks describes that weird Miesian dematerialization of solid stuff. Mies' concentration of architectural vision beams out of his eyes like X-ray vision, vaporising the corner of buildings so that enclosing walls seem only like planes, emptying city blocks so that gigantic buildings and plazas feel as lightly arranged as still lives. Chicagos history of chaotic freedom and incarceration is mutely articulated through Mies' architecture.

As Mies left Europe behind, he left a country and a continent full of ideological problems. America, comparatively, was new, was innocent, and was only just coalescing as an urban form. In the vernacular grid of Dodge City, perhaps Mies saw new possibilities of his formal and highly architectural use of the grid that had obsessed his urban visions. There is an intersection between an American pragmatism and an intellectual European avant guard. And this unlikely paring built big and raw in Chicago.

Having first arrived in New York, Mies was drawn to Chicago because of pragmatic issues - looser controls on architects licensing, and the offer of a job as head of the AIT architecture school. But perhaps there was something else. Perhaps Mies recognised something of himself in the flat plains and the gigantic skies of the Midwest. That strange Miesian absence in comparison to the dense narrative of his native German countryside - a sentimental and nostalgic narrative which had become central to Nazi symbolism. Perhaps he saw in a landscape made up of city grid, the flat expanse of Lake Michigan and the plains stretching out beyond the horizon a vision of nothingness that mirrored his architecture of reduction.

His Chicago projects might be read as remakings of this landscape. The Federal Centre plaza remakes the midwestern plains as a grid of tiles - a plainer plain, with a flatter horizon, and a bigger sky, with corn and dust abstracted away. The regular joints between the tiles encouraging an exaggerated sense of perspective. A big flat space for the wind to blow across.

At Lake Shore Drive he made cliffs for Lake Michigan. As iconic and immovable as the White Cliffs of Dover but shorn of sentimental narrative, a blank silhouette against the shore.

As well as versions of nature, other projects in and around Chicago are about the modification of nature by architecture. The boiler room became the centre of the IIT campus, as it should always be if we could only think clearly enough. After all, it is the thing that enables all of these buildings to be habitable during the freezing winters. It's the heated water flowing through pipes that allows all of this architecture to happen. It's the thing that modifies nature into architecture.

This idea is developed at Farnsworth House, in rural Plano in what Peter Smithson describes as "ruburb" - a mixture of rural and urban. The house is as invisible as architecture can be. A glazed box with no internal walls and a central service unit that houses all of the servicing. Essentially, it is a raised platform of temperature controlled air, with sanitation and running water held between two slabs of whiteness. As though the winter snows have been quarried like the marble of the Barcelona Pavilion.

The Farnsworth House is nice, its cute, its luxurious. It's small and desirable. The Federal Centre, IIT and Lake Shore Drive are hard to like. Their beauty is almost invisible - we need to be guided to understand it. And it feels like it's our fault - for not noticing, for not looking or thinking enough. Mies' architecture recedes behind a veil of everyday banality.

When you see the piles of dirty snow piled up on the plaza of the federal Centre, the photocopied notices sellotaped to the walls, you see the logic of architecture verses the logic of badly organised, underfunded, unenthusiastic, wishing it was on holiday life. Abstraction lapped by endless waves of dull narratives of everyday banality. The ever-growing blobs of chewing gum dotting over the grid like spits of rain before a storm. The metal detectors at the entrance to the Federal Building as additions to an architecture which couldn't foresee backwoods white supremacists or fundamentalist religious opposition to the rational bureaucracy of democracy. The A4 printouts taped to the marble elevator lobbies are additions and modifications to Mies' architecture. Since Mies left the building, the life that fills it every day has added to the architecture. Forming like a crust over the surface of the building. Interrupting, diverting, these are part of an architecture that is entirely opposite to the completeness of Miesian vision. They are ad hoc, amateur, ephemeral, unaesetheticised, confused. From missing persons notices to gonks on top of monitors, we've made something new out of Mieses place.

Small yellow plastic cones that warn us of wet floors as the teams of cleaners that polish Mies's vision. And perhaps the cleaners are the only people who use the building in an appropriately Miesian manner - schedules of floor polishing, timetables of bathroom cleaning, the regular and precise application of cleaning products to the surface of the building - spraying, wiping, sponging, sweeping, sucking. The same regular human actions choreographed through out the landscape of the building. And what they are removing is the dirt, the spills, the crumbs that have fallen, the detritus of activity. Wiping up the coffee breaks, bits of salad dropped from a lunchtime sandwich, piss from the floor, and shit from the bowl. Straightening piles of paper, rewinding the building to its immaculate state, returning the building into beautiful Architecture.

Like Prohibition, temperance and abstinence motivate Mies' architecture. And just like Prohibition, the attempting to exclude behaviours only serves to highlight our vice. Mies' Chicago landscapes are a kind of sober architectural or urban "lack". It's only through our use of them that they become part of and engaged with the city. Perhaps we should recognise our own creative co-authorship of Mies' architecture, encourage the build up of ephemera across the surface of the buildings. Somewhere between the extremes of confused intoxication of ephemera and the rational sobriety of architecture that the essential uniqueness of these places can develop.

Mies, you cut precise slabs of marble from the earths crust, you rearranged iron ore into long straight lines. You took the ground and made it new. Stacked things one top of the other lined things up next to each other more neatly than anything had ever been stacked.

Mies. Forgive us. Mies, we couldn't handle abstraction, we wrote banal stories across your plazas, around your lift lobbies. Maybe our only excuse is that we had to live. That we couldn't resist eating French Fries, that we felt an uncontrollable lust, that we were too lazy, too dishonest, too busy, too human.