This illustrated reference takes readers on a revealing tour of a vital, underappreciated piece of our nation's infrastructure.

Imagine Washington, D.C., without its clean and effi cient Metro. Or New York City without the Lincoln and Holland tunnels. Or Boston without the Big Dig. This nation without its tunnels would be a quagmire of clogged streets, urban gridlock, massive sewage and water pipes along our sidewalks, and train routes that would take hours longer just to veer around a mountain instead of going straight through it. Unlivable.

Tunnels have been built for 200...