After more than 10 years of work, the round-the-clock project is on budget and on time, Mehdorn said, to open at the end of May, two weeks before the start of the soccer World Cup that will bring more than a million extra visitors to Germany.

"The light at the end of the tunnel is definitely getting brighter," said the chief executive of rail operator Deutsche Bahn during a viewing tour of one of the German capital's biggest construction sites.

"A load will drop off our minds when that station is finally finished," he said, raising his voice to be heard above the pounding of hammers and the whine of metal cutters.

Loved by some, loathed by others, the former Lehrter Bahnhof station is nearing the end of its estimated 700 million euro (480 million pound) transformation from a World War Two ruin to one of Europe's key rail hubs.

The massive station, near the chancellery building and within sight of the Reichstag parliament's glass cupola, has become a sightseeing stop for both visitors and Berliners.

But its fame is tinged with notoriety partly because of public complaints about the location and partly because of a dispute between Deutsche Bahn and the architect, who says the rail operator mutilated his design by changing the ceiling.

The station's strategic importance is not in doubt: with the World Cup looming, it will play a crucial role in getting teams, equipment and media from game to game across the country.

It is believed to be Berlin's most expensive building site by yearly investment and the biggest European rail intersection for east-west and north-south trains.

"Berlin can really be proud of this station," said Mehdorn. "This will be the envy of many cities."

"TORSO"

Deutsche Bahn expects some 300,000 people to use the station every day, with 1,500 local, national and international trains scheduled to depart daily.

The building was designed by Meinhard von Gerkan, one of Germany's most famous architects who, with his partners, also designed the roof on Berlin's Olympic Stadium.

The relationship between Gerkan and Deutsche Bahn started to sour after the rail operator decided some years ago to cut the outside roof spanning the east-west tracks by a quarter to 320 metres (1,050 feet) to reduce building time.

Gerkan said this reduced the station to a "torso."

But the builder's decision to change the ceiling in the 450 metre-long (1,476 feet) and 60 metre-wide (197 feet) underground hall, where north-south trains will stop, really angered him.

Gerkan accused Deutsche Bahn of harming his architectural copyright by changing the ceiling, which had been designed to arch and undulate cathedral-like over platforms and tracks.

"This is probably the biggest underground hall worldwide and it looks like a supermarket ... run-of-the-mill," said Gerkan, after Deutsche Bahn installed a flat, grey metal ceiling.

"This is just pure disfigurement. I cannot believe that a builder would mutilate his own project," the architect said.

A court now has to decide if the ceiling should be changed back to the original design. It is not known when that ruling might be delivered.

"THE BIG EMPTINESS"

Others have more pragmatic objections to the project.

Berlin's Lehrter Bahnof in 1879

The site in the former no man's land at the intersection between east and west Berlin is rich in history -- but some argue it is anything but handy for Berliners.

The front of Lehrter Bahnhof in 1911

It was at Lehrter Bahnhof station that Germany's first chancellor, Otto von Bismarck, bid farewell to politics in 1890. Nearby is the place where Guenter Litfin was shot dead in August 1961 by East German guards as he tried to swim to the west -- just 11 days after the Berlin Wall was erected.

Lehrter Bahnhof 1948

Unlike other main central stations, there are no houses huddled around the tracks and some of the newly built tarmac streets around the station are virtually empty.

Berlin's daily newspapers dubbed the station "the centre of nowhere" and "the big emptiness", questioning how useful it would be for the city's residents who might struggle to get there because of poor links to the local transport network.

Mehdorn rejects these arguments.

"A station like this is only possible because there wasn't anything else, because it was a sand desert," he said.

"We are not building this station for the soccer World Cup, we are building it for the next 50 years."

Gerkan agrees that the station is more than a traffic hub.

"This station is the business card of Germany."