In the sixteenth century, chronic wars and a high concentration of towns made the Low Countries one of Europe's prime laboratories for innovations in military architecture and urbanism. The 1553 inspection tour of the region by engineers Giovanni Maria Olgiati and Sebastian van Noyen marked the assimilation of “Italian-style” fortifications into Netherlandish practice and the transition there from defenses with bastions to proper bastioned systems. Olgiati and Van Noyen's joint tour is well documented through a dozen design drawings now held at the Vatican Library, Turin's Archivio di Stato, and Madrid's Palacio Real, as well as a closely related atlas in Turin and complementary archival records. As Pieter Martens discusses in Planning Bastions: Olgiati and Van Noyen in the Low Countries in 1553, these materials, including many hitherto unknown plans, provide new insights into the design process, offer a unique panorama of the Low Countries' border defenses at this critical moment, and illuminate the genesis and spread of bastioned fortifications in Europe.