On 17 October 1919 King Alfonso XIII of Spain inaugurated the capital’s first ever subway line. It went from under the Puerta del Sol in the center of the city up 3.48 kilometers north to Cuatro Caminos. A century later, the fledgling underground transport system of a measly eight stations boasts 12 lines and 302 stations, spanning 294 kilometers. It is the third longest subway in Europe, and the world’s eighth. It is a vanguard of accessibility with its 1705 escalators and 530 lifts. It has always run on electrciity, even long before saving our Planet via the clean-air route has become an urgent task!