A collaborative research program, known as PCR, is currently studying the architecture of buildings associated with the Templars and Hospitallers in the old county of Champagne and Brie and its surrounding areas, spanning the 12th to 16th centuries. The project is being led by Vincent Marchaisseau and Cédric Roms from Inrap, a French research institute specializing in archaeology and historical heritage. The team includes a range of experts such as Arnaud Baudin, Jean Bernard, and Gabrielle Sheehan, among others. The study builds on a decade of prior research at the Avalleur commandery in Bar-sur-Seine, Aube, where similar architectural remains have been examined. The geographical focus of the study is the old county of Champagne and Brie, which in the 12th century included parts of modern-day Champagne and several ecclesiastical territories, including the dioceses of Chalons, Langres, Meaux, Reims, Sens, and Troyes. The research includes dozens of surviving medieval structures, such as chapels, residences, barns, dovecotes, fencing elements, and fortified towers. These buildings were primarily constructed at the end of the Middle Ages and were built under the Hospitallers, a military and religious order that succeeded the Templars after their dissolution in the 14th century. The research program is divided into three main areas of focus. The first examines the historical conditions under which these commanderies were established, including the use of historical documents like visit reports, which were official inspections of the orders' properties. The second area focuses on the geographical and topographical placement of these commanderies, analyzing factors like environmental conditions, access routes, and circulation patterns. The third area is dedicated to the architectural study of the buildings themselves, aiming to understand their chronological and spatial development and to explore how these sites evolved after the Hospitallers took over the assets of the Templars. The fortification of these commanderies is a topic considered separately, as it generally occurred later, after the 14th century, and is linked to the turbulent times of the late Middle Ages and the Renaissance. This period saw events such as the Hundred Years' War and religious conflicts that influenced the need for stronger defenses. The study also includes urban sites, such as parts of the Reims commandery preserved in the Le Vergeur Museum, offering a glimpse into the architectural legacy of these military orders in the region.