Berlin has gone virtual. As of Thursday morning, the German capital - from the gigantic Alexanderplatz TV tower right down to the potholes in the side streets -- can be seen in Google Earth. The virtual visitor can even enter the new Berlin Central Station and marvel at the Reichstag. Other landmarks are likewise on offer.

For now, the pixelated metropolis is largely unpopulated. There are no virtual politicians wandering the government quarter and no virtual shoppers strolling Unter den Linden. It will be a few years yet before online cities like Berlin get mashed up with computer worlds like Second Life.

But 3D Berlin is more than just a pretty computer project. Already, there are those dreaming of online shops occupying the same address in the virtual world that their real-world sisters occupy in real life -- and with the same wares on display. Indeed, it seems that the virtual parliament buildings, embassies and election campaigns on Second Life are little more than a test run for the digital version of the real world that Google, Microsoft and others are in the process of building.

In order to see Berlin 3D, you need to have the newest version of Google Earth and must access it through this link.

Berlin has proven a willing partner, having supplied the site with content free of charge. Represented by the Business Location Center Berlin-Brandenburg, the German capital commissioned a 3D model of itself from 3D Geo -- which it then made available to Google.

"It's a new dimension to innovative location marketing and investor incentive," says Harald Wolf, Berlin's Senator for Economics, Technology and Women's Issues.

Berliners are taking particular delight in having beaten their rival Hamburgers to the chase. On January 17, Hamburg announced it would be the first city in the world to present itself in 3D on Google Earth. The press conference featured a virtual helicopter flight over the city; viewers floated over Hamburg's city hall and its famous historic port.

Google spokesman Stefan Keuchel praised the realistic textures of the facades, obtained using aerial shots of the buildings. He promised that Hamburg 3D would be going online "in a few days or weeks." Evidently he promised too much -- the program is still not online. Data protection issues have delayed the project indefinitely.

The result for Berlin is impressive. Some 44,000 buildings in Berlin's city center can be seen in the simple view, though the facades are not the real ones. But a complete virtual city tour, coupled with historic narration, is soon to come. Some 550 buildings of particular significance have been singled out with photos of their facades.

A further 50 buildings and building complexes are represented in greater detail. Most novel of all, however, is the attempt to bring virtual visitors inside. Users can wander through the Reichstag, check out the new Berlin Central Station, marvel at the stunning interior of Frank Gehry's building next to the Brandenburg Gate, and visit the Sony Center and Olympic Stadium.

Five especially prominent buildings be entered virtually and viewed from the inside: the Reichstag (German parliament), the central train station, the DZ Bank on Pariser Platz, the Sony Center and the Olympic Stadium.

Further improvements are sure to come. The race is on for the best 3D city in the world.