This updated edition asks some great questions. When did people first build tunnels? Where is the world's longest tunnel? What keeps tunnels from collapsing? You'll find the answers to these questions and many more in Building Amazing Structures. Each book in the series looks at some of today's most amazing structures from around the world. Begin your journey by reading about similar structures in history and how they were built. Then discover the techniques and materials that today's engineers and builders use to make even more amazing structures. Finally, learn about structures that failed and why.