"Thought-provoking fare to launch deeper research." - Booklist 

"Cutaway views reveal a dazzling worldwide gallery of vaults, tunnels, shelters, and excavations in this work translated from Spanish...Explanatory captions and well-chosen inset details illuminate finer details of construction and design" - Kirkus

K-Gr 5–"This fascinating history of underground construction marvels takes ­readers from earliest times to the present in a chronological journey through gargantuan human feats of engineering. The colloquial tone is spare and humorous, with an eye on innovation through the ages. Beginning with the “Tunnel of Contents,” chapters include the ancient (1100–300 BCE) walls of rock and caves in Cornwall, now the United Kingdom. “Over the years, it has been pillaged by collectors and nosy people,” which means there’s not much left to discern its use. Best guesses are the low-ceilinged, narrow tunnels may have been burial sites or grain storage. Surely, the rocks were dragged from distant quarries, which testifies to incredibly hard work in ancient times. Works include the Gadara (Jordan) Aqueducts in the 1st century; the 12th century Dover Castle; Spiral and Tijuana Narco Tunnels; the Seoul Subway; the Chunnel Tunnel between England and France; and even the White House Bunker in Washington, D.C. Most unusual is the Svalbard Global Seed Vault, which preserves agricultural biodiversity in case of global wars and is built into the rock to withstand floods, earthquakes, volcanic eruptions, or other disasters. Located on a remote Arctic island, the temperature is kept at zero degrees ­Fahrenheit to avoid contaminating seed samples. Many other incredible big digs with superb illustrations will galvanize students and inspire pre-engineering aficionados. VERDICT Highly recommended for its compelling content, global inquiry, and stunning ­illustrations." –Lonna Pierce, School Library Journal

"The future architect will love this book, a detailed look on the various underground tunnels and structures across the globe.” -Youth Services Review

“Informative and approachable, this book highlights some of the most intriguing underground marvels of human creation, and it is a positive addition to library nonfiction collections for upper elementary school-aged readers.” - Mary Lanni Reads

"Hand this to a budding architect" - YA Books Central 

"It's a good fit for my library, since I have a specific group (a daycare/after school program) that likes books on architecture and engineering to use as inspiration for the kids to build models and this will add some great ideas for them to try out. - Flying Off My Bookshelf

"From the Large Hadron Collider to secret tunnels under cities and buildings, the book’s colorful artwork and vibrant illustrations makes for an involving, alluring creation that will attract picture book students and leisure readers alike." - Donovan's Literary Services

"Sanchez focuses on high-interest aspects of each construct, including fascinating trivia alongside basic information in the accessible explanatory text and captions. Big Digs is great for kids to flip through and explore or read with an adult (who will no doubt enjoy it as well)!" - Glass of Wine, Glass of Milk