Just how high does a building have to be to qualify as a highrise? The definitions often vary: for some, it's more than 10 storeys, for others, higher than 70 metres, and for the more dramatic, as soon as the building has an elevator. To take it a level further, when can a tall building call itself a skyscraper? In the Netherlands, we set that bar at 100 metres. That is relatively modest compared to the Burj Khalifa in Dubai, the world's champion standing at 828 metres. The appeal of cities seems to be undying and inner-city housing is often in huge demand. Is living at a (high) altitude the solution to this problem? And what effect would that have on us?