Two boys stumble upon the remains of an ancient underground civilization.
- ISBN10 0812472551
- ISBN13 9780812472554
- Publish Date 1 June 2002 (first published 31 December 1987)
- Publish Status Out of Print
- Out of Print 13 September 2021
- Imprint Perfection Learning
- Format Hardcover (Library Binding)
- Language English