The 40,000km-long Incan road system connected 12 million people, but it also supplied the Incan army with food from thousands of storage depots spread across the whole network.
At its largest, the Inca Empire spread from modern-day Ecuador down Peru and Bolivia to Chile and Argentina, and was home to 12 million people. Civilisations of this size require a sophisticated communication and transportation system to defend their borders and stay cohesive – like the Roman roads, the Persian Royal Road, or the Chinese Imperial Highway. The Inca had some rather unique challenges though, namely how to travel the Empire, much of which was in the longest mountain chain on the planet, without wagons, chariots, or horses.
(Side note for you sticklers: the Andes is the longest mountain chain above water; you can count the mid-ocean ridges if you want but no empires have needed to navigate them so far.)
The road network of the Inca was interspersed with thousands of tambo and qullqa. Tambo were kind of like inns, places where imperial travellers could sleep, cook, and eat. Qullqa, aside from being a Scrabble player’s dream word, were storehouses for food such as freeze-dried potatoes. The tambo were spaced one day’s walk apart from each other (around 22km), so you could pretty much walk from Ecuador to Argentina without needing to hunt or borrow food from the locals.
(Another side note for you sticklers: I know there’s only one Q tile in Scrabble. Obviously I’m referring to Super Scrabble, or certain versions of the Latin Scrabble tile set.)
The qullqa would have mainly served the administrators, army, and rulers of the empire rather than the residents of the areas they passed through; once the empire fell they mostly dropped out of use. Thousands of ruined qullqa can still be found across the Andes.