Guanajuato's unique tunnel network consists of former riverbeds converted into roadways after dam construction in the 1960s. The longest tunnel stretches 3 kilometers and follows the original course of the Guanajuato River. These tunnels were blasted using dynamite, utilizing expertise workers gained from decades of mining operations. Today they form a complex labyrinth of underground roads that makes Guanajuato unlike any other city in the world.