Patterns in Peru: An Adventure in Patterning, by Cindy Neuschwander

(Henry Holt & Co. 2007; ISBN 0-8050-7954-8)

The Zills Family is visiting Peru to study an ancient woven tunic that is connected to the mysterious Lost City of Quwi. Matt and Bibi would love to find the Lost City, but they get separated from their parents and stumble into a bigger adventure then they'd ever imagined.

With only each other, their dog, Riley, and the unusual patterns on an ancient tunic to guide them, the twins must use their understanding of patterns and sequences to locate the Lost City.