It took me a long time to realise this, but the Centre Pompidou is pure Archigram.
Archigram (http://archigram.net/index.html) were a group of 1960s architects who were trying to think outside the conventions, and in particular to embrace technology. Their schemes included a walking city and the plug-in house: when you needed more space, cranes would deliver add-in units to connect up to the service core.
In 1963-4 I shared a flat with three architecture students who used to bring home the free sheets that Archigram used to put out. For years I saved them (sometimes using them in school), and then, like so much else, decided they were of no further interest and threw them away. (Big mistake.)
(The following year, while I started my teaching job, my equally utopian friends, with a sense of mission caught from their hero Le Corbusier, went out to build streets in the sky -- tower blocks -- for local authorities.)
Archigram projects were characterised most obviously by exposed structure and services. That's exactly what's most striking about the Centre Pompidou by Renzo Piano, Richard Rogers and Gianfranco Franchini (design 1971, opening 1977). These circulation tubes and external walkways could be straight from an Archigram scheme:
as could this exposed structural engineering:
But is this any different?
Those flying buttresses are shamelessly displayed structural supports; the east end of Notre-Dame is a 13th century Pompidou Centre.
But saying they're structural isn't saying they are not expressive. They certainly are that as well; we feel them as well as seeing their purpose. To us (21st C) they perhaps look like the membranes of a web-limbed extra-terrestrial; to an overawed medieval worshipper, what? organic forms, vegetal, straining upward and inward - to support, but also to grasp?
But the Pompidou, too, is expressive. The tubes and pipes and struts and bracings serve functions, but the decision to display them was rhetorical -- they aren't out there because they need to be; there are perfectly good ways of accommodating mechanical functions without making a show of them (and incidentally while protecting them from the corrosion the Pompidou's steelwork is showing).
These elements aren't just being technology; they're saying technology, making a style or language out of its elements. Pretty exciting too, to my mind.