Big Digs: Amazing Underground Constructions

BIG DIGS is an interesting look at underground structures that have been built over time and around the world. It begins with ancient structures in Cornwall where tunnels were made underground thousands of years ago through modern times and into ideas for life on Mars.

What I loved: Every page is fully illustrated and does a great job depicting the underground structures with lots of cool details. They provide a lot of clarity on what it looks like and how it is used. The accompanying text is conversational and easy to understand, answering the basic questions readers might have like how it was made or how it was used. The breadth of locations and times was great, giving a fantastic glimpse into history, architecture, and construction.

The book is very large, which makes it fun to lay out on the floor and explore. Some of the call-outs add contextual information about culture or the time that add to the fun and provide additional learnings that are fun.

What left me wanting more: As a small thing, some of the text is very small and can be hard to read on dark backgrounds. Younger eyes will have an easier time of it though. The information touches upon a lot of topics without going too much in-depth, so it may be a good platform to then find other books with more detail about specific topics of interest.

Final verdict: BIG DIGS is an interesting look into underground structures over time and the globe that will entertain curious middle grade readers with detailed illustrations and conversational text.

Who knew that there were so many underground tunnels, or that they were built over such a long period of time?! From prehistoric tunnels in Cornwall and ancient aqueducts to a Finnish nuclear waste repository built in 2004, this book describes a variety of different underground construction projects from all over the world.

Underground architecture is hard to depict, but Sánchez does a good job at showing cross sections of the buildings, which can't have been easy. I did appreciate that there was sometimes a building on the surface that was shown, when it has the entrances to the tunnels. Of course, now I really want to know how anyone was able to map out the tunnels under Dover Castle, although I'm not surprised that they were used as bunkers during World War II.

The variety of uses for these tunnels is interesting. There is the global seed vault in Svalbard, the Big Dig in Boston, and the Hadron Collider, which are all very official, but also Narcotunnels in Tijuana, tunnels under the Berlin Wall, and the very odd Quinta da Regaleira, a personal palace built by a man who was a Freemason. There is one underground installation that is no more: the Presidential Emergency Operations Center (PEOC) (1942-2001) that was destroyed in the fall of 2025.