HONG KONG'S buildings have made a habit of stretching away from the rest of the Asian pack in recent years. Central Plaza and the Bank of China tower are the two giants of the region. It is symbolic that Hong Kong has been one of the spearheads of the Asian push towards the top of the economic ladder and that two of the tallest buildings in the world outside of the United States are in the territory. But within a few years they are going to lose their positions as the top two. Sky Central Plaza in Guangzhou, climbing 80 storeys and 402.5 metres, is tipped for the top when it is completed in 1995. But, a year later, Malaysia will take the biggest step. Kuala Lumpur's Petronas Towers will reach 450 m, making the twin structures the tallest buildings in the world. Sears Tower in Chicago, at 443 m, has been the tallest building since it was built in 1974. The World Trade Centre and the Empire State building come a close second and third at 417 and 381 m respectively. Wan Chai's Central Plaza still stands pretty tall by comparison at 374 m. The Bank of China is six metres smaller. But none can compare with the mother of all skyscrapers - Tokyo Ecopolis City 1000. Last year, a consortium produced a plan for the massive building which will reach an incredible 1000 m, that is if it is ever built. It would house 75,000 residents. Before Ecopolis, another company was seriously tossing around the idea of a 500-storey skyscraper. The Taisei Corporation went higher, in concept at least, when it proposed the four-kilometre-high X-Seed complex. That is higher than Mount Fuji. Builders in Japan said towers could stretch as high as 200 floors using today's technology, but the country's plot ratios needed to be relaxed. The push towards the clouds is expected to continue because developers want to make the most of areas of land they acquire because of the increasing expense. Environmentally, there are two sides to the coin. One side argues that the buildings take up less space, therefore allowing more areas for parks and lakes. The other says that a huge increase in infrastructure is needed to support these gigantic structures. Inside modern sky scrappers, hi-tech equipment reduces the risk of serious fires. Evacuation procedures and well-designed stairwells keep risk of injury to a minimum. Marketing and leasing of these buildings is usually well underway before the building has been completed. Rents go up with the building, particularly in Hong Kong where a good harbour view commands a high premium. Higher land costs appear to be ensuring that the super skyscraper is here to stay. No doubt, more giants will be appearing on the skylines of the world's major cities for some time to come. The big players are going to keep thinking bigger.