Skyscrapers are playing a more and more important role in modern life and definitely more and more tall buildings will be built in the future. But at the same time they are facing more threats from terrorists, fire, earthquake and other unforeseeable factors than before. This paper presents the idea of providing a secondary evacuation system in tall buildings, as a supplement to the existing primary means of evacuation especially when they are damaged or unusable in an extreme event. It illustrates the design flaws inherent in high-rise buildings today and the inadequacy of their primary evacuation systems and introduces some new mechanisms currently used as a secondary evacuation system. The paper thus serves as an introduction to this area and produces some useful advice for increasing the safety of tall buildings.