London on London

In 1902 American author Jack London visited London, England, and lived incognito for several weeks on that city's East End among its poorest and most crowded inhabitants. He described his time there in The People of the Abyss (available, free, from Project Gutenberg, here).

Here's a sample from that report, concerning the phenomenon sometimes called "London fog":

“Leaving out the disease germs that fill the air of the East End,
consider but the one item of smoke. Sir William Thiselton-Dyer,
curator of Kew Gardens, has been studying smoke deposits on vegetation,
and, according to his calculations, no less than six tons of solid matter,
consisting of soot and tarry hydrocarbons, are deposited every week
on every quarter of a square mile in and about London. This is
equivalent to twenty-four tons per week to the square mile, or 1248
tons per year to the square mile. From the cornice below the dome
of St. Paul’s Cathedral was recently taken a solid deposit of
crystallised sulphate of lime. This deposit had been formed by
the action of the sulphuric acid in the atmosphere upon the carbonate
of lime in the stone. And this sulphuric acid in the atmosphere
is constantly being breathed by the London workmen through all the days
and nights of their lives.

Although significantly reduced by clean-air programs dating from the 1950s, London fog, renamed "smog," still bedevils the city, with automotive exhaust replacing the smoke from the last century's coal-burning engines.