A wide variety of sources enables those interested in investigating the indoor-school history. A major source of visuals to be taken advantage of are old postcards, as shown here. The Vives indoor school of the La Fère cavalry district in Aisne is a typical example of a military school built in the 19th century in a cavalry district or barracks. These buildings were classified into three categories based on their size by a 1861 circular. First class, the largest, included areas 52.50 m long and 21 m wide.