Underground cities, a staple in science-fiction, are rarely found in reality due to the considerable engineering constraints involved with their construction. I wondered if such a city could be excavated in one continuous pass by one tunnel-boring machine, to minimize digging time and surface impacts, and the result is a side-by-side coiled tunnel leading to one above-ground entrance building. The whole city can be thought as one long street with one-story houses/stores on each side, regularly interrupted with shortcuts to reduce travel time.