Get a rare glimpse into places that are usually out of sight! The Underground Worlds series uses detailed cutaways and illustrated diagrams to show the layout and purpose of various underground structures and systems. Find out how they were designed and built, the challenges they presented in construction, and the innovative technologies that have made building underground possible. When more space was needed in Helsinki, Finland, environmentally friendly planners looked downward rather than outward. They dug a "shadow city" into the rock below to house many of the city's services. Underground Cities uses cutaway illustrations of subterranean city spaces built and used by people, including underground salt mines, wartime bunkers and tunnels, shopping malls, and pathways built throughout the world. Book jacket.