The Herrenknecht company specializes in tunnel-boring equipment. Last year, it sold three of its enormous drilling machines to Mexico, where they are to help solve an equally massive problem: the inadequate drainage and wastewater system of Mexico City.The Mexican government is building what will be the world's longest wastewater tunnel, the 62-kilometer Tunél Emisor Oriente. Our four-part series by Alexa Meyer and Patrick Benning describes the challenges faced by the engineers and the tunneling crew. The first episode shows the assembly of the first boring machine in Germany and describes the consequences of frequent flooding on the inhabitants of the Mexican capital. The tunnel project is in a race against time to protect the city against catastrophic future flooding.