Nearby, other British architects are working away. Lord (Richard) Rogers is finishing off three highly sculptural blocks - two of offices, one of apartments - in the architectural turmoil of the vast Potsdamer Platz development, right on the line of the former wastelands of the Wall. A few hundred yards away, Will Alsop's Anglo-German firm Alsop and Stormer has used collage techniques for the facades of its Stresemannstrasse office block. And over near the former border crossing of Checkpoint Charlie, a younger Anglo-German outfit, architects Matthias Sauerbruch and Louisa Hutton, are building one of Berlin's few new towers - a slender, ecologically advanced HQ for the city's state housing agency.

Rogers' blocks at Potsdamer Platz

All these things have taken huge amounts of time and effort, and not just because of wrangles over land ownership in a post-Nazi, partly post-communist, city. Berlin, despite being in recent years the world's largest building site outside China, is far from being a stylistic free-for-all. The authorities frown on anything that departs too much from the inherited and rather turgid 19th century pattern of large, low, urban blocks. When the city came to be re-planned in the aftermath of German reunification, many a free-thinking design to rebuild its devastated centre - by Alsop and Rogers, among others - was declared out of order by some very buttoned-up city planners. It is to the credit of the Italian architect Renzo Piano, who eventually became masterplanner of the largest chunk of the Potsdamer Platz district, that anything of merit has emerged from the vast reconstruction programme there.

Although four tall buildings, by Piano and others, have been allowed at Potsdamer Platz to relieve the monotony (and make money), his achievement is more to do with the new streetscape than it is to do with the qualities of individual buildings. Piano's shopping mall, for instance, while tumultuously busy, is scarcely mould-breaking - you could be anywhere in the world. And while his old chum and former partner Richard Rogers's blocks alongside try their damnedest - not since the Pompidou Centre of 1971-76 in Paris have these two worked so closely together - Rogers could only take his modelling knife to the standard planner-approved Berlin block shape and carve away the flanks as much as he dared. Alsop's building is even more conventional. The only fun is in the patchwork nature of the facades with their slightly wilful mix of materials and neon strips.

Libeskind: Jewish Museum

Knowing the constraints, you wonder at first how Daniel Libeskind's Jewish Museum, a great metal-clad zig-zag that breaks all the rules and was famous years before it opened, ever got built. Go there, however, and it's immediately obvious why. It is what real estate agents would describe as "off-pitch" - well away from the historic and now rebuilt centre, stuck out in a dreary inner suburb of social housing projects and dual carriageways, and moreover partly hiding behind the restored wedding-cake architecture of the old Berlin Museum. It's big and it's daring, laden with all the powerful symbolism that Libeskind - Polish-born, Berlin-based, Jewish - can muster, but it is undeniably parked in a corner of town where it poses little threat to the status quo.