Imagine a particularly intricate and improbable piece of engineering that would uproot the Statue of Liberty, pedestal and all, from New York Bay and place it on top of the Burj Khalifa.
Now take a second Lady Liberty, all 93 metres of her, and balance this on top of the first. Only now do you have a structure to match the height of the proposed Kingdom Tower in Jeddah.
Due for competition by 2018, the Kingdom Tower will not just snatch the crown of the world's tallest building from Dubai, but also become the first building to rise above 1,000 metres.
Side by side, the two buildings could be sisters, soaring towers of glass that rise from a wide base to a needle spire that seems to pierce the sky. But their design is not the only thing they have in common. When it comes to the tallest of the tall, these days location is as important as engineering.
Earlier this year the Council on Tall Buildings and Urban Habitat released its annual report for 2012. The organisation, which studies trends in city architecture, is based in Chicago, a city once celebrated for its skyscrapers.
These days, though, the council must cast its net a little wider than the Windy City. and even far beyond the shores of the United States.
Three out of the five tallest buildings competed last year were in Dubai, led by the 413 metre Princess Tower in Dubai Marina, which is also the tallest residential skyscraper in the world. Dubai also boasts the tallest hotel in the world, the 355 metre JW Marriott Marquis Dubai which opened last month.
Seven of the top 20 were in China and three in Saudi, including the year's biggest, the 601 metre Makkah Clock Tower, one of only two buildings to be awarded "megatall" status by the council.
Other cities in the top 20 include Panama and Hanoi, while Abu Dhabi made it with the completion of the Nation Towers on the Corniche. But only one North American city can claim a place in the top 20: The Trump International Hotel in Toronto, down in 15th place.
As Dr Anthony Wood, the executive director of the CTBUH, points out, 2012 actually saw a slight decline in the number of tall buildings finished, something he attributes to the continuing impact of the world recession.
Yet at the same time, last year was still possibly the second most successful in history for skyscraper completion.
Dr Wood describes the pattern in the Middle East as: "Interesting." The global downturn hit construction in places like Dubai hard, yet the city is still up there. What has happened, says Dr Wood, is that initially "work stopped or slowed on buildings that were half way through competition. Last year saw a lot of those buildings finished."
In general, though, while cities like Dubai and Abu Dhabi continue to push upwards, much of the future construction will take place further east, in Asia.
In countries like China, tall buildings are an effective way of housing large numbers of people, as the population migrates from the countryside to the cities. In the Middle East, tall buildings are more of a statement of intent. The Burj Khalifa, says Dr Wood, is part of "A financial model based on a making a grab for business and tourism."
In that sense, the Burj represents Dubai's push to become a world city, and the costs of its construction need to be set against that bigger picture. At the same time, the 829 metre tall structure, which includes apartments and a luxury hotel, is not simply an expensive marketing tool for the Emirates. The "wow" factor of being in the shadow of the tallest building on Earth has pushed up land values all around the Burj, creating an economic ripple effect that benefits the whole city.
Much the same is true of the Kingdom Tower, although its immense height will capture most of the headlines. The building uses a wide base to support the structure, rising to a narrow point.
It is a design pioneered by the BurJ Khalifa and works well in buildings designed primarily for residential use because it places less demand on the internal structure, particularly the need for multiple lift shafts to move large numbers of office workers sumultaniously.
For buildings like the Kingdom Tower, the CTBUH has created a new category of "mega-tall" structures that are over 600 metres. There are currently only two in the world, the Burj Khalifa and The Makkah Royal Clock Tower. The Kingdom Tower will be the third, but others are expected to follow. Oil-rich Azerbaijan has announced plans for a 1050 foot tower to be completed by the end of the decade.
Dr Wood says the limitations on the height of a building are financial rather than structural. "One mile, two miles, three miles? Technology is not an issue. The comparison is with putting a man on the Moon. It can be done. Whether it should be done is another matter."
By 2020, the CTBUH estimates that eight "megatall" structures will be complete, headed by the Kingdom Tower and the Burj, but with the addition of the Ping An Finance Centre Centre in Shenzen, the Seoul Light DMC Tower in South Korea, the Signature Tower in Jakarta, the 623 metre Shanghai Tower and the Wuhan Greenland Centre.
Of the top 2020 in seven years time, 14 will be in Asia. From the West, the most spectacular new skyscraper will be the 1776 foot tall One Trade Centre in New York City.
With a height designed to recall the date of the Declaration of Independence, One Trade Centre replaces the old Twin Towers, destroyed in the terrorist attacks of 2001.
The new structure is 124 metres taller than the old World Trade Centre North Tower, which at the time was the tallest building in the world when it was completed in 1972.
It is a sign of the new world order of "megatalls", that One World Trade will rank only 12th in the world rankings - barely half the height of the Kingdom Tower.
Yet as Dr Wood points out, while the West may not dominated the skyline anymore, western technology still drives skyscraper construction. And that expertise may be put to new use in the future.
With the exception of the Twin Towers, no building over 200 metres - and there are now over 700 such structures in the world - has even been taken down. The tallest building to be voluntarily demolished was the 186 metre Singer Tower in Manhattan, taken down in 1967.
In the future, says Dr Wood, we will need to think not just about demolition but also preservation. "We will need to design these buildings with a lifespan of hundreds of years," he predicts.