Cover: The Undersea Grizzly Bear Helmet (Museum Object #NA5739, Penn Museum Image #151906) was collected by Penn Museum Curator Louis Shotridge in 1917. The helmet, dated ca. 1770–1790, is Tlingit and comes from Klukwan, Alaska. It is made of wood, pigment, spruce root, human hair, abalone shell, and copper. Shotridge wears a similar helmet on page 12 of this issue.
A Marvel of Maya Engineering: Water Management at Tikal
Peter D. Harrison
Hidden Earthworks in the Forests of the Bolivian Amazon
John H. Walker
A New Look at What in the World?