If for some reason you are trying to look up the average heights of people in various countries, you’ll quickly find that the tallest countries are in northern Europe or the Balkans, where men are just over 6 feet on average and women are around 5″7. The shortest are certain poor countries, such as Bolivia, where men average 5″3 and women between 4″8 and 5″0 feet.
I don’t know if these statistics are correct (the 4″8-5″0 range given for Bolivian women is suspiciously imprecise, for example). Even if they are accurate, you may have noticed that they do not really answer the question. These statistics are giving the heights of adult men and women. But, of course, not everyone is an adult, and not all countries are split equally between men and women.
If (again, for some reason) you are interested in finding the true heights of countries, you have to adjust for children and gender. Once you do this, you realize that the country with the shortest people on average is probably somewhere like Niger, where 50% of the population are under 15 years old. The country with the tallest people on average is probably somewhere like Qatar, where men outnumber women 3.4 to 1 and where only 14% of the population are under 15 years old. The true average height of Niger may be something like 4 feet; the true average height of Qatar may be something like 5″6.
[Actually, these estimates are probably way off too, since they do not take into account babies. The tallest places are presumably those which have had the fewest babies in the past year or so, and the shortest places those which have had the most].
This same adjustment can be applied to cities: the megacity of Lagos (in Nigeria, not Niger) is 50% children, whereas Tokyo is 12% children. Las Vegas, especially on the weekend, is perhaps the tallest — the most male and the most adult — big city in the United States, somewhat similar to the glitzy desert cities on the Persian Gulf coast.
Now, does knowing this have any real-life utility? No. But it might be cool if a city like Lagos were to build, say, a low-ceiling double-decker bus that only kids could comfortably use.