The Great Quarters
A quarter is not a district. Districts are administrative and every city has them; a quarter is a name people give as an answer to where they live, and it carries information the postcode does not. This collection holds cities where at least one such name has outlived the reason it was given.
The mechanism is usually a single decision, taken once and defended for two centuries. Belgravia was laid out by Thomas Cubitt from 1826 on the Grosvenor family's marshland, to one design, with stucco terraces and garden squares that the estate still controls through leases; Mayfair and Knightsbridge came from the same landowning logic on the same side of the same park. Paris did the reverse — Haussmann cut boulevards through everything, and the quarters that survive as names, Faubourg Saint-Germain and the streets behind the Étoile, are the ones the cutting spared or created. Vienna's Innere Stadt is what the walls left when they came down in 1857.
Some quarters are made by a wall of a different kind. Shanghai's former French Concession keeps plane trees and lane houses because a foreign administration zoned it that way before 1943, and the trees are now protected. Cairo's Zamalek is an island. Mumbai's Malabar Hill is high ground in a city that has almost none. Hong Kong's Peak was reserved by ordinance for Europeans until 1946, which is an ugly origin for the most expensive residential ground in Asia and is not softened by leaving it out.
The American and Latin quarters are younger and were sold rather than inherited. New York's Upper East Side became what it is after Central Park opened and the Fifth Avenue mansions followed the park north; Buenos Aires' Recoleta grew around a cemetery when yellow fever drove the wealthy out of the south; Mexico City's Polanco and São Paulo's Jardins were laid out in the 1920s and 1930s as garden suburbs and were swallowed by the cities they were built to escape.
What the twenty-six have in common is that the name survives independently of the boundary. Nobody can say precisely where Belgravia stops. Everybody knows what it means.