How many people can you fit inside of a given amount of land area? This is a tricky question to answer, to give a good answer you would need to ask a number of other, related questions. For example can you have people on top of one another in three dimensional space and if so, how high? Do they need room to breathe, eat, sleep, work or engage in other activities needed to survive?

So the previous question is, for the most part not really answerable and will just get you silly and unrealistic answers. However this does raise another question: What is the highest population density that has ever been achieved in the real world?

The answer to that question was the Kowloon Walled City, aka the City of Darkness or the City of Anarchy, a Chinese exclave inside British Hong Kong. The entire slum had by the 1990’s a population of around fifty thousand confined within a mere two and half hectares of space. This was a shockingly high population density of approximately two million people per square kilometre! Manhattan, the most densely populated region of the United States has almost one hundred times less density than this Chinese city.

How did they do it? Well basically they built tiny, one bedroom rooms, often without any adherence to building regulations and then they crammed five or six people into each of those rooms. Then they stacked all these rooms all on top of one another for fourteen stories above ground (building higher than this was dangerous due to low flying aircraft that were landing or taking off from the nearby airport).

Combine these cramped apartments with very narrow corridors filled with leaky pipes and a near complete lack of natural sunlight for most of the residents and there you have it, the most densely populated place in all of human history. The entire city, for decades became notorious for being a haven for drug dealing, prostitution, dog eating and most infamously: unlicensed dentists.

The entire city was however demolished in 1993 as it had by this time become an embarrassment to both the British and the Chinese governments. A park had been placed on what remained of the area, complete with a model of the former city so that we would always remember what once existed there.