Population density of Gotham

Saw, very belatedly, Dark Knight Rises.  Didn't like it, for what almost inconceivably little that's worth.

However, I did have real problems with the cutting-off of Gotham City.  Bane blows all the bridges and traps, he says, twelve million people on the island. That's problematic.

New York has a population of 8.2 million.  OK, Gotham is bigger. But that's greater New York, the five boroughs; Manhattan - the bit that could be isolated - has a resident population of 1.6 million. It depends, I suppose on the day it happens; midweek, there are four million. For it to be 12 million it has to be three times as large as Manhattan or three times as dense. That's not impossible, I suppose -  that's the density of the lower East Side in 1910 - but in a non-1910 environment it's difficult.

By comparison, there were three million people in Leningrad during the siege  there in WW2 and half a million and up died. That was much longer, of course, but it does give some idea of the number of people you need to enforce something like that; a large part of an army group, something like a couple of hundred thousand trained people with tanks.

The problem is the gigantism of the scriptwriter. Four million would have been more than enough - enough, as it is, to starve within a week unless there was continuous boat and helicopter traffic, enough to be uncheckable by the pitifully few gunmen Bane commands.

The problem lies at the core of the superhero mythos (and the Star Wars mythos, with the Jedi) - There just aren't enough of them to make a difference, whatever their powers. But there's no need to make it worse by inflating the numbers.

I did recognise some bits of Pittsburgh.