This visual series will explore the secret places, treasures, and histories hidden beneath our feet. Each book will dive into the origins, construction or formation, science, and purpose or importance of underground sites. Historical, geographical, and cultural context will intrigue young readers to learn about the events, people, and findings that make these underground places unique. Aligned to Common Core standards and correlated to state standards. A&D Xtreme is an imprint of Abdo Publishing, a division of ABDO.