An alternate way to measure size is to look at urban footprints from space which gives us a rough and ready comparison, if not of population then at least of how far the concrete sprawl reaches. Below is São Paulo's satellite footprint:
|São Paulo's 18,850,000 residents as seen from above|
And if you know the area well you will be able to identify Serra da Cantareira, Parque Estadual da Cantareira, Sao Paulo Guarulhos International Airport, Tiete River, Taiacupeba reservoir, Guarapiranga resevoir, Represa Billings, Reserva Estadual and Represa Pedro Beichi.
Interestingly the spread of the city is very expansive despite large parts of it being highly verticalised. To contextualise here's a comparison with other large cities all shown on the same scale: Madrid, Buenos Aires, Shanghai, Mexico City
|Madrid, 4,072,000 strong but a small village compared to São Paulo|
|São Paulo's nextdoor neighbour is also a giant with 13,170,000 residents|
Shanghai from above (population 16,650,000)
|Mexico City, 20,450,000 and Latam megalopolis|