The Gulf state of Dubai has unveiled plans for the world's tallest building, the latest in a rash of projects to aim for the altitude title.
It will be tall, but no one will say exactly how tall
Construction of Burj Dubai, which will contain homes, shops offices and at least one hotel, could get going within two months, according to the developer, state-controlled Emaar Properties.
Emaar has released artist's impressions of the tower, but remains cagey about its exact size.
Until more detailed plans are published in March, the firm will say only that Burj Dubai will be taller than the Petronas Towers in Kuala Lumpur - currently the world's tallest building - and a larger proposed skyscraper in Shanghai.
Such coyness is understandable: competition in the skyscraper market is becoming fierce.
Burj Dubai is a prestige project, designed to add lustre to a vast redevelopment of the Gulf state.
Emaar alone is involved in eight huge projects, notably an ambitious plan to develop the world's largest man-made marina.
Dubai is currently investing billions of dollars in infrastructure in an attempt to secure its future as the commercial centre of the Gulf region.
In 2000, it opened the world's first seven-star hotel, and is now pouring its efforts - and $5.5bn - into the biggest artificial island ever constructed.
A crowded market
Whether it can hold on to the crown for the world's tallest building is another matter.
Predictions that skyscraper construction would be stalled after September 11 have come to nothing - indeed, some projects seem to have been brought forward.
Dubai is investing billions in its marina
Foremost among these are competing designs to replace the World Trade Center in New York. Both proposals aim to out-top the Petronas Towers by a wide margin.
Work has just begun on the Shanghai World Financial Centre, and similar-sized buildings are planned in Hong Kong and Taiwan.
Even on Dubai's doorstep, two lofty skyscrapers have gone up in the Saudi capital, Riyadh.
The wrong sort of tall
Clouding the issue is the vexed question of what constitutes a building.
At 553 metres, the CN Tower in Toronto, Canada, calls itself the world's tallest building, but is disqualified by extending its height with a spike.
The Petronas Towers, like the Dubai and Shanghai skyscrapers, is inhabited right to the top.
The distinction is necessary to differentiate genuine buildings from TV masts and other structures, which can often be far taller than the highest office block.
Last month, an Australian power company unveiled plans to build a solar tower that will exceed 1,000 metres in height.