Shanghai runs on two apps you don’t have yet.

What it is

Shanghai is China’s largest city and its financial centre — around 25 million people, on the Huangpu river a few miles inland from where the Yangtze meets the sea. That position is the whole explanation: it is the point at which the largest river system in China meets the ocean, and everything the city has ever been follows from it.

The river splits it in two. Puxi, on the west bank, is the old walled town, the former foreign concessions and nearly everything historic. Pudong, on the east, holds the towers — and was farmland and warehouses within living memory.

How it got here

Shanghai was a walled county town of no great importance until 1842, when the treaty that ended the First Opium War forced it open to foreign trade. Britain, then France and the United States, took territory along the river and governed it themselves: the concessions, which were not colonies but were not China either.

What grew there over the next ninety years was one of the strangest cities in the world — a treaty port with its own police, its own newspapers in a dozen languages, no passport control, and a skyline of banks along the Bund. It was the fifth-largest city on earth by the 1930s. It was also where the Chinese Communist Party held its first congress, in a lane house that still stands.

War ended it. Japan occupied the city, the foreign concessions were surrendered in 1943, and after 1949 Shanghai spent forty years as an industrial city that the rest of the country drew on and did not reinvest in. The Bund’s banks became government offices.

Then in 1990 the state designated Pudong — farmland across the river — a new development zone, and what followed is probably the fastest transformation of any major city in history. The Oriental Pearl went up in 1994, the Jin Mao in 1999, the World Financial Center in 2008, the Shanghai Tower in 2015. People still working in those towers were born before the ground under them was anything but fields.

What it is known for

Shanghai is known for the Bund and the skyline facing it across the water; for being the place China does business; for a cuisine that is sweeter and more soy-heavy than the rest of the country and for the two dumplings everyone confuses; for lane houses and plane trees; and for a pace and a self-confidence that Chinese people from elsewhere comment on immediately.

What visitors tend to remember is smaller: how completely the phone replaces the wallet, how safe it is late at night, and how much of the best of it costs nothing at all.