In Part 4 of Engineering the Inka Empire: A Symposium on Sustainability and Ancient Technologies, John Ochsendorf presents Engineering in the Andes: Indigenous Suspension Bridge Technology. The Inka Empire relied on an extensive network of roads and bridges to connect the various regions under Inka control. Though the Inka road system has been studied in some detail, scholars have largely neglected the role of bridges. These functional works enabled the expansion of the Inka Empire and often dictated the location of roads, tambos, and other Inka sites. The role of bridges in Andean history raises important questions and demands greater attention from historians of the built environment. Due to the detailed chronicles of the construction process, suspension bridges provide a unique opportunity for understanding the organization of construction in the Inka Empire. This presentation draws on primary source material from chroniclers' descriptions of the bridges to identify important Inka bridges, explore their origins, and pose questions for future research in Inka engineering.John Ochsendorf has been on the faculty at the Massachusetts Institute of Technology since 2002, and is the Class of 1942 Professor of Architecture and Civil and Environmental Engineering. He earned his Bachelor of Science in structural engineering and archaeology from Cornell University, where his undergraduate thesis carried out the first technical study of Andean suspension bridges. Ochsendorf earned a Master of Science in Civil and Environmental Engineering from Princeton University and a PhD in structural engineering from the University of Cambridge. He is a founding partner of Ochsendorf DeJong and Block LLC, a consulting firm specializing in historical structures. He has won numerous awards for research in structural engineering and architecture, including a Graduate Research Fellowship from the National Science Foundation, a Fulbright Pre-Doctoral Scholarship from the J. William Fulbright Foundation, a Rome Prize from the American Academy in Rome, and a MacArthur Fellowship from the John D. and Catherine T. MacArthur Foundation.This symposium was webcast on November 14, 2013 from the Rasmuson Theater at the National Museum of the American Indian in Washington, D.C.