Why rebuild a palace when you have no emperor? The question of imperial redundancy is at the core of the strange rebuilding of Berlin’s Stadtschloss, the vast palace that was once the centre of the city.

The new-old palace has endured a long and expensive rebirth and is now ready to open to the public when Covid restrictions are lifted (a partial opening on December 17 had to be delayed). Yet a building which awkwardly combines Prussian Baroque and stark rationalism with undertones of fascist architecture is a curious statement in a country that, having come to terms with its history, sees itself as modern, industrial, technocratic and cosmopolitan.

The rebuilt palace will be the home of the Humboldt Forum, a new institution incorporating works from two older museums, the Ethnological Museum of Berlin and the Museum of Asian Art , as well as a new exhibition dedicated to the history of the city and expansive educational facilities. At €663m it is one of Europe’s most expensive new cultural buildings in an era when expensive cultural buildings have gone a little out of fashion. Walking through the new Stadtschloss, it seems to be more about itself than its contents.

The problem here is absence: the absence of a clear purpose, of an emperor and of the building that this reimagined pile of stone-clad concrete replaces, the Palast der Republik. That showpiece of East Berlin and the GDR was a symbol of another vacuum, the absence of democracy. It was a mix of rubber-stamp parliament and leisure centre, a bronze-tinted-glass and marble showcase of the wonders of socialism aimed both at locals and the west.

The original Stadtschloss, begun in the 15th century and hugely expanded by Frederick III (later King Frederick I of Prussia) and architect and sculptor Andreas Schlüter from 1699, was left in ruins after the second world war and in 1950 it was demolished. It left a huge hole in the city centre which initially became the bleak Marx-Engels Platz, a public parade ground for soldiers and tanks.

In an effort to create an image of progress, the Palast der Republik was opened in 1976. With its mix of formal and informal uses and its mirror-tinted glass surfaces, the Palast that replaced the palace was a strange building - comparable, perhaps, to London’s Festival Hall in its status and to a Texan suburban office campus in its aesthetics. As well as the powerless parliament, the Volkskammer, it housed two auditoria, a theatre, more than a dozen restaurants and cafés, a bowling alley and a disco. It was one of the few places in the city where citizens could get a decent cup of coffee or use a payphone that probably worked.

The Palast became inscribed in the everyday lives of East Berliners as they attended official events, degree ceremonies and informal meetings with friends. But it was never clear that it was loved. Until, that is, its demolition was proposed in 2003. The official excuse for flattening the building was that it was riddled with asbestos, though many other buildings from the same asbestos-infatuated era have been adapted and seem to work just fine. East Berliners suspected that this was part of a project of westification rather than reunification, the elimination of all traces of a regime that had framed so many lives. Despite their objections the building was demolished in 2006, with no clear plans for what should replace it.

The idea of rebuilding the Stadtschloss was promoted by businessman Wilhelm von Boddien, who set up an astonishingly successful campaign. Private donors contributed €80m of the cost, and the city agreed to the reconstruction.

Much of Schlüter’s original statuary had survived in various museums and courtyards and that has been reinstated, while the rest of the elevations have been reconstructed to original plans and photographs. The new stonework has been machine-cut from digital drawings and its precision looks a little frosty — though the contrast with the eroded fragments of the original, weather-worn statuary neatly reveals the artifice.

If the rebuilt facade is impressive in its detail, the entrance foyer is underwhelming, a bleak white box pocked with a few of Schlüter’s more fragile sculptures, a pair of angels suspended from the plasterboard above a provincial corporate doorway. Other original statues stand atop plinths, their surfaces bearing traces of history, weather and war. If you were being generous, you might find a touch of Wim Wenders’ Wings of Desire in them.

The courtyard, however, is on another level. The ceremonial centre of the court is an undeniably impressive sight, some fragments of original stone bearing the traces of both (Russian?) graffiti and cataloguing from when they were stored. A new Uffizi-style external courtyard is intriguingly attenuated, introducing a hybrid classical/corporate language.

The atrium is intended to anchor the new institution, acting as a public forum, performance and reception space. It is here that you become fully aware of the work of Franco Stella, the architect who won the competition to rebuild the palace. Stella is a devotee of Italian rationalism, the local version of modernism which was heartily adopted by the Mussolini regime and was resurrected in a Postmodern vein in the 1980s by architects including Aldo Rossi and Vittorio Gregotti.

Severe and occasionally brilliantly inventive, the style continues to be influential. You might ask whether it works here. As a restrained framework for the Baroque theatrics, it might look fine. But those heavy undertones of fascism in a reconstructed imperial palace in the centre of Berlin are unsettling. Not only here in the atrium but in the facade facing the river Spree. The Stadtschloss’s architecture attempts, I think, to create a neutralised classicism, shorn of detail but not historic association. Yet the effect is chilling, a cold 21st-century riposte to the Greek-inflected, soot-stained buildings of the neighbouring Museum Island.

Inside, the Humboldt Forum is a vast 42,000 sq metres. I was told it has more exhibition space than the whole of the Museum Island. Its exhibits were being installed when I visited and it would be unfair to judge except to say that it is, of course, made to fit the grid of the reconstructed facade, which has led to some curious spatial contortions: floors taken out, intrusive mezzanines, and so on.

The exhibitions themselves have already generated controversy, including one over the display of a collection of Benin bronzes bought from the British. When the decolonisation of institutions is in the air, the reconstruction of Kaiser Bill’s imperial palace with a crucifix on top looks insensitive at best.

There is a sense inside that the palace is too big and too grand for its contents, a rather random collection of collections. Surely it will settle in to become part of the city’s cultural and physical fabric, but questions remain over whether this was what the city needed.

Berlin has proved extremely good at adapting existing structures for new uses but somehow a blindness has set in over the communist legacy. The Palast der Republik was a museum in itself, realising a modernist dream of creating an urban living room of culture and communication. It would have been much more interesting to see what architects might have done with that, rather than with a reimagined, brand new building.

Both buildings are, in a way, fake facades. The Palast der Republik presented an image of democracy for the German Democratic Republic. The newly rebuilt Stadtschloss pretends it never happened. Both are about the stamping of a political identity on the city and both attempt to obliterate what came before in equally ruthless ways. The palace now sits at the dead centre of Berlin and has created exactly that: a dead centre.