Collective memory is special everywhere, but nowhere more so than in the German capital, writes Frank McDonald, Environment Editor

How things are remembered, or rubbed out, in the German capital can be very controversial - whether it's the new Memorial to the Murdered Jews of Europe or the plan to demolish the GDR's Palast der Republik.

It is now 16 years since the Berlin Wall was breached and publicist Lea Rosh started her campaign for a Holocaust memorial. Since then, almost all of Die Mauer has vanished, virtually without trace, and an area of more than four acres in the "death strip" that lay behind it has been developed as a Holocaust memorial.

The location, just south of the Brandenburg Gate, could not be more visible. Right beside where the US is building a new embassy, and within sight of Norman Foster's dome on the Reichstag, it was selected specifically to express the memorial's public character, underlining the fact that it is "addressed to civil society".

Approached from the green oasis of the Tiergarten, architect Peter Eisenman's memorial appears as an undulating labyrinth of limestone slabs (or stelae), each one the same dimensions in plan but none appearing to be the same height. It is only when you get close that you realise they're all made from the fairest of fair-faced concrete.

Laid out on a grid, this Stelenfeld (field of stelae) gives no clue to its depth when viewed from a distance. It is only when you see people disappearing into the maze or walk through it yourself that you realise some of the standing stones are more than four metres high, all inclined at angles of between 0.5 and 2 degrees.

There are no inscriptions or symbols, other than plaques around its edges requesting visitors to observe a set of rules - no music playing, no eating or drinking, no roller-blading or skate-boarding, etc. "I fought to keep names off the stones, because having names on them would turn it into a graveyard," Eisenman has said.

The New York-born architect, who is also Jewish, was chosen to design the Holocaust memorial in 1998 by Helmut Kohl, then German chancellor, following the failure of a competition to produce a result. His scheme for 2,711 stelae took advantage of the site's area and topography; the number itself has no symbolic significance.

Daniel Libeskind did a garden filled with 49 tilted concrete stelae at the Jewish Museum in Berlin - 48 to represent the year in which Israel was founded and the 49th to represent the city itself. His name is also emblazoned all over the museum, in an egregious display of ego-mania which Eisenman has studiously avoided in the Holocaust memorial.

The grid pattern allows visitors to enter the memorial from all sides and choose their own route through it, along undulating pathways made from open-jointed concrete paving stones. You progress from street level into the centre where looking up "earns a mere glimpse of sky between the towering concrete forms", as its architect said.

"An overwhelming sense of disorientation is increased by the askance tilt of each stela. The intent is that the visitor, who finds himself winding his way through the concrete forest of varying heights, will be struck by how distant the busy city centre seems, and how quiet and reflective - but not graveyard-like - the atmosphere is."

Engineers Buro Happold developed the construction process to manufacture the huge numbers of stelae. Made from toughened concrete, with a surface as smooth as glass, each one was treated with an anti-graffiti agent which - controversially - was supplied by a company that once made Zyklon-B for the Nazi gas chambers.

At the south-eastern corner, not far from the site of Hitler's bunker, there is an underground museum documenting the Nazi genocide of European Jewry. Including this museum, the overall cost of the memorial is €27.6 million. Separate memorials are being built in Berlin to commemorate the gypsy and homosexual victims of the Holocaust.

Much more understated but equally moving is the monument in Bebelplatz, beside Frederick the Great's Staatsoper, to commemorate the infamous Nazi book-burning of May 1933. Designed by Micha Ullman, an Israeli-born installation artist, it is invisible until you stumble across its ground-level glass window in a vast stone-cobbled square.

Beneath is a white room lined on all four sides by empty white bookshelves. Best seen after dark, it was unveiled in 1995 and later removed and reinstated after a car-park was built under the square. A simple plaque records poet Heinrich Heine's prescient words from 1820: "Where books are burned, in the end people will burn."

Across Unter den Linden, beside Schinkel's Neue Wache, is the glorious baroque Zeughaus (Arsenal). It used to house the GDR's German History Museum and is currently being fitted out for the same use, using a somewhat different narrative, starting with a new annexe designed by the Chinese-American architect, IM Pei.

It has a particularly eye-catching staircase tower, which seems to swirl in motion against the backdrop of the original building, with its (authentic) new pink hue, and the smooth French limestone of the annexe.

It's called the Pei-Bau (Pei Building), which is not surprising for an architect who copyrighted images of his pyramid at the Louvre. Not far away, straddling the east bank of the River Spree, stands the Palast der Republik, the former GDR parliament, which was built in the mid-1970s. But this symbol of the old regime is doomed. After Fractale, an alternative art show finished there last Saturday, the ugly building with what's left of its bronze-tinted glazing is due to be demolished.

What irks Wolfgang Thierse, president of the Bundestag, who has made a mission of its demolition, is that the Communists blew up the war-damaged Berliner Stadtschloss (city palace) in 1950, because they saw it as a "symbol of Prussian militarism".

So now he wants to pull down the Palast der Republik that ultimately replaced it.

But the Palast der Republik was not just the seat of the Volkskammer (people's chamber), it also housed bars and restaurants, a theatre and even a bowling alley.

What's more, it was used as a venue for civil marriages; many east Berliners have wedding pictures of themselves on the grand staircase of the white marble foyer, which was lit by 1,001 lamps.

Closed in 1990, ostensibly because it contained asbestos, the interior has since been stripped down to its massive steel beams and trusses, making it an eerie place for an art exhibition.

The structure is so solid that it seems ridiculous to pull it all down and sell the steel for scrap. A new façade is all it needs, rather than an ersatz rebuilt Stadtschloss.

However, just as the GDR attempted to rewrite history by getting rid of the original building, there is an equivalent determination - at least in some quarters - to do the same in Berlin nowadays, even though the city is groaning under the weight of a debt of €59.7 billion from all the urban renewal it has witnessed since the wall came down.

Most transformed of all is Potsdamer Platz. Before 1990, there was nothing here but hillocks, rabbit holes and dead-ends, plus a few surviving buildings. Now it has all been redeveloped, with skyscrapers, office buildings and an attractive shopping centre, characterised by an architectural diversity that won't be seen at Spencer Dock.