It would be the end of the story if the 60-storey Commerzbank were simply another corporate filing cabinet in the sky sheathed in a shiny skin of stainless steel or clad portentously in marble. It would the end of the story, too, if this were purely another exercise in corporate one-upmanship: my prestigious headquarters is more prestigious than yours. After all, there is nothing new or daring in constructing buildings that scrape the sky. The reverse if often the norm: most high-rise offices built over the past 30 years are lacklustre, missing the Olympian quality of Manhattan's Empire State Building or the cinematic charisma of its eternal rival, the Chrysler Building.
The Commerzbank, however, is different, and, if this doesn't sound silly given its Brobdingnagian scale, a small step forwards towards a new generation of skyscrapers. Foster has designed the tower from the inside out, so that unlike 99 per cent of skyscrapers that consist solely of identical floors stacked one above another and linked by an eerily viewless lift, the Commerzbank boasts a fairly complex interior and one much to the benefit of the 2,400 Deutsche-suits who will amass towering piles of money here.
It differs from the archetypal filing cabinet in the sky because its tall triangular core is punctuated by internal hanging gardens that spiral up and around it. These sky gardens, one for each floor, have been planted initially with mature olive trees and acacias, and will mature into lush aerial groves, bringing Nature and softened sunlight into the heart of this steely money machine. Staff will be able to open windows (yes, opening windows, an astonishing late 20th-century achievement) and look out through a green veil to the city beyond their computer screens.
Foster has long talked of overthrowing the tyranny of high-rise office blocks by creating "sky lobbies". The hanging gardens in the Commerzbank take the idea a stage further. Why should those working to make huge profits for banks be denied plants and flowers? Or fresh air?
This is what makes the Commerzbank almost special. Otherwise, it is a fairly routine job for Fosters and Ove Arup & Partners, the engineers. In fact, in certain ways the tower is a bit of a disappointment. Its facades, although well finished, are routine; unlike, for example, Foster's superb headquarters for the Hongkong & Shanghai bank (1979-86). The way the Frankfurt tower meets the street is also a little hackneyed, crash-landing in an awkward stone-clad podium block designed to respect the existing street (but more to comply with the dictates of the city's planning authorities), without conviction or panache. The building comes into its own only as it reaches above the existing city roofscape.
From Taunusanlage or Gallusanlage, the two parkland walks that follow the line of Frankfurt's medieval walls, the Commerzbank is undoubtedly the finest of the city's all but anonymous towers. These walks are not much fun at night, by the way; they are haunted by outsized German junkies, and best avoided. Yet, from these vantage points, Foster's articulated tower goes a long way towards redeeming the skyline of the city Germans like to call Bankfurt, or, with a nod to its underlying architectural conceit, Mainhattan; the city straddles the River Main, which feeds into the Rhine.
Yet, compared to Manhattan, Frankfurt seems anodine and tame. Part of the problem (if it is a problem) is the fact that planners insist on having new developments follow the old street layout. As this was destroyed (as was half the city) by bombing in two tumultuous air raids in 1944, its ghostly, yet insistent presence is evoked more by nostalgia than common sense. This nostalgia appears to have grown with the years, so that although Frankfurt's "South Bank" boasts a string of smart new museums, the old centre has seen the reconstruction of schmaltzy Hansel-and-Gretel timber buildings in the shadow of the priapic, yet unfeeling banks. If a city wants these money machines, it should let rip with them, confining them to a particular quarter without hemming them in by a corset of planning restrictions rooted in a misplaced nostalgia.
Easy to say, perhaps, when you live in London, a city that was badly bombed but nothing like half-destroyed. Yet despite Frankfurt's celebrated museums, its lively drinking hausen (where off-duty bankers get sozzled on jugs of ebbelwei - apple wine), its upbeat club culture and fondness for all things American, the city's reason-to-be at the end of the 20th century is money. Germany's first stock exchange opened here in 1585, and this is where Mayer Amschel Rothschild founded his pan-European financial empire. Today the city is host to somewhere between (depending on who you listen to) between 388 and 426 banks.
At the time the stock exchange was founded, the city walls were punctuated by no fewer than 42 towers. They have long gone, to be replaced by what seems like (I forgot to count them) an equal number of "Mainhattan" skyscrapers. The Commerzbank is the best of them.
With luck, the principles informing this new building will gradually feed their way into the minds of British developers and planners. In terms of ecological thinking, the Germans are a long way ahead of us determinedly dirty Brits, who like nothing more than to spend our working days cooped up in energy-guzzling buildings, remote from Nature and safe in the knowledge that we are doing our bit to help global warming. The Commerzbank shows that big may not be especially beautiful, but it can be responsible. What we need now is to see the same or similar principles applied to a corporate headquarters without compromise, and see how far it is possible to create an ecologically sound skyscrapern