Since the London “Metropolitan Railway” was opened in 1863 the subway has become a symbol of urban life. Tun – nel systems are the lifelines of the big cities, transporting millions of passengers every day. The success story con – tinues to this day, with existing networks being continu – ally expanded and completely new systems being planned and built especially in the Asia and the Arabian world. Beginning with Hector Guimard’s Jugendstil entrances for the Métro in Paris, the design quality of the stations has always been an important aspect. With design, light – ing, furnishings and frequently with artistic interventions, the underground complexes made of tracks, platforms and accesses have become the subject of great spatial creations. This volume provides an overview of the highly interesting and manifold current trends in underground construction around the world.