Evidently in Hong Kong, remaining buildable land = 0.
Large scale projects were not built in Hong Kong, but on land strips and islands the former colony has learnt to colonize. Ironically, some of these "colonies" came at the cost of slicing up the city's own flesh. The fragments that appear as an intact city, are held together only by a delusion blurred amidst soaring skyscrapers and extensive infrastructure, where the city itself is nowhere to be seen.
In the size of a city, the ambition of a 7-million population parallels a country. This airport island could have existed between any two speckles in the South China Sea. In fact, in the very near future, I propose the Empire of Hong Kong.