The first step to constructing a skyscraper is digging a big foundation hole. When the Petronas Twin Towers were built in Kuala Lumpur, Malaysia, Engineers had to shove massive concrete pillars 60-120 meters into the Earth's bedrock layer. The second step to building a skyscraper is making its steel skeleton. This is just like the frame of a car. Strong iron or metal beams are welded to create long vertical columns. At each floor level, these vertical columns are connected to horizontal beams. The third step also involves building the steel skeleton. This steel frame has outer walls (or curtain walls) that support almost all the weight or the building. The weight from all the floors gets transferred directly to the vertical columns. This sends forces through the steel skeleton down into the building's base. In modern skyscrapers, these exterior curtain walls are made almost entirely of glass which gives more floor space for tenants to live or work. Once the skeleton has been built, the fourth step is much easier. The floors are then added to a new skyscraper, often one to two a day. A fifth and final step is stabilizing the skyscraper. Some buildings have huge weights controlled by computers. The weight glide back and forth in the opposite than that which the building moves during an earthquake or high winds.