Cities and populations
For some reason I find it interesting to look up populations of cities. Here are some ballpark figures from Wikipedia, so I don’t forget.
(city name - population of city / population of area - city population density per km2)
Tokyo JP - 8M / 12M - 5700 New York NY USA - 8M / ? - 10200 London UK - 7M / 14M - ? Los Angeles CA USA - 4M / 16M - 3000 Hong Kong CN - 7M - 6200 Yokohama JP - 4M / ? - ? Osaka JP - 3M / 17M - 12000 Chicago IL USA - 3M / 10M - 5000 San Francisco CA USA - 800k / 7M - 6400 Singapore - 5M - 6000 Houston TX USA - 2M / 5M - 1300 Auckland NZ - 1.2M / ? - ? Christchurch NZ - 360k / ? - ?
See also: wikipedia’s list of most densely populated cities.