Big Digs by Kiko Sanchez

For thousands of years, people have been building great structures, such as the Egyptian pyramids and the Golden Gate Bridge, but there are equally great structures that are mostly out of sight. Some underground structures are every bit as grand and difficult to build as any on earth. This book looks at 20 incredible underground structures around the world and explains what is known about their use and methods of construction. Some of those shown are expected, such as the Chunnel Tunnel and the Big Dig in Boston, but some are not commonly known, such as the Drammen Spiral and the Temple of the Feathered Serpent. All are fascinating. Each has its own spread with several paragraphs explaining why the structure was built, some of the methods used, and, in some instances, the discovery of it. Beautiful, detailed illustrations show the structures in cutaway views to give readers a real sense of the size and difficulty of building such a thing. The writing is conversational and appropriate for young readers. A glossary at the end will help middle-grade readers with some of the unfamiliar terms. This is a real winner.