Most cities grow outward. Chongqing grows in every direction at once.

Perched on mountains at the junction of the Yangtze and Jialing rivers, the city has had to solve the same problem repeatedly: how do you connect a metropolis when flat land is a luxury? The answer is layered infrastructure stacked across cliffs and hillsides - roads running through buildings, metro lines emerging from skyscrapers, bridges that double as city blocks.

Locals call it an "8D city," shorthand for the disorienting sensation that gravity has its own agenda here. A building's ground floor on one street is its fifteenth floor on the one below. The Liziba metro station cuts straight through a residential tower between floors six and eight.

With over 30 million people in the metropolitan area, Chongqing is one of the largest cities on earth — and one of the least understood outside China. It rarely makes the lists that Shanghai and Beijing dominate, which is part of what makes it worth watching.