Discover underground cities around the world, including who built these cities, why they were built, and more!

Did you know some cities are built underground? They could be hidden just beneath our feet! In Hidden, Lost, and Discovered: Underground Cities, you'll uncover where these cities are hiding and the secrets they contain!

The Hidden, Lost, and Discovered series explores some of the most interesting places around the world, that some people don't even know exist! Eye-catching photographs, hidden histories, and fascinating facts will pique the interests of readers in this high-interest, lower-reading level series.