When we talk about the world’s largest cities, they’re always vertical 21st-century megalopolises straight out of a Mission: Impossible movie: the neon of Tokyo, the smoggy sprawl of Mexico City or L.A., the canyons of New York, the space-age skyline of Shanghai. But when my ten-year-old son asked me the other day what the world’s largest city was, it turned out he didn’t care about population numbers. He wanted to know what the biggest city was in size—that is, by area. The answer, it turns out, takes us to the grasslands of Inner Mongolia and the remote Chinese “city” of Hulunbuir.

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Hulunbuir is the northernmost region of Inner Mongolia, just west of Manchuria in northeastern China. It’s a sparsely populated grassy plateau, where camels roam and yurt-dwelling families tend their herds of cattle, goats, and sheep. It’s one of China’s loveliest and most unspoiled bits of wilderness.

But Beijing officially designates Hulunbuir as a “prefecture-level city,” even though its urban center, Hailar, has only a quarter of a million people (about the size of Fort Wayne, Indiana) and is just a dot in the middle of the region’s vast wilderness. But Hailar doesn’t have city limits—officially, it’s an urban district within the “city” of Hulunbuir. Hulunbuir’s city limits make it about the size of Great Britain—and larger than 42 U.S. states—but, by Chinese law, that’s the size of the city.

So by this (official but admittedly somewhat silly) definition, Hulunbuir is the world’s largest city—bigger than Tokyo and New York and London and all the rest—even if it has more camels than cabs and more shepherds than shoppers. Other countries can boast similar “big cities” in underpopulated areas. The City of Kalgoorlie-Boulder, in the Australian Outback, is run by a mayor and city council even though it covers more area than Portugal. Altamira, a Brazilian “city” in the Amazon rainforest, is the size of Illinois.