Find out about secret tunnels past and present. Secret bunkers, underground cities and war-time tunnels - it's all in here. Then read a story about treasure, a secret tunnel and a secret exit. This book is part of 'Thunderbolts', a series of 24 levelled reading books covering popular non-fiction topics. Published by Ransom Publishing, a specialist in books for struggling and reluctant readers, the 24 full-colour titles offer progression over four levels and low level language. Each book features a non-fiction section together with a fully illustrated fiction story on the same topic. Secret Tunnels is part of Set Three.