What were the many uses for the Paris Underground over the course of history as noted in the nonfiction book, Underland?

The space beneath the city has had many uses throughout history. Built on limestone, the catacombs were first created by miners who mined the limestone for Paris' buildings. Later, Paris filled the caves and caverns with its dead. When the catacombs filled up with dead bodies, they had to be excavated. Later, the chambers were used for mushroom farming. French resistance fighters hid in the tunnels and caves during WWII. Today, a large group of people explore and hang out in the underground city, forming a subculture with its own rules.