Over a hundred elaborate scale models, some as big as a Paris apartment, were created by engineers to help French monarchs scheme their plans of attack with a god’s-eye view. Dating from 1668-1870, this extraordinary collection was nearly destroyed when their home at the Louvre was converted into a museum for art.

The project of building miniature versions of key fortifications began under the rule of Louis XIV, the Sun King, and continued under Louis XV. One hundred fifty sites were reproduced with painstaking accuracy, usually created on-site by the Corps de Fortifications, then moved into the collection upon completion. They were primarily built of plaster, papier-mâché, and wood, at a scale of 1:600, or 1 inch to 50 feet, with key monuments often slightly scaled up in proportion. Each model was built onto custom interlocking tables, which allowed them to be transported and reassembled for the king. The creators were obviously not content to merely create a passing likeness of each location as they are intimately detailed, many with added flourishes created by adding materials scavenged from the original site.

Louis XIV housed and showed off the collection at the palace at the Louvre. By the time the Louvre was re-purposed in 1774, it had largely passed into disuse and the dusty models were nearly discarded. Luckily, in 1777 the collection was moved into its present home at the Hôtel des Invalides on the orders of Louis XVI — a fitting site, originally built by the Sun King as a home for disabled soldiers who fought in the wars he planned with these very models. Twenty years were dedicated to the preservation and reconstruction of the aging miniatures.

For decades the collection remained stagnant, but then under the post-revolutionary Empire it saw new action. Napoleon (whose tomb you can also visit at les Invalides) saw the distinct advantage that these unique aerial views could provide, and promptly commissioned mock-ups of his newly conquered lands and fortifications. His team’s access to newer surveying technology created remarkably accurate models.

The last models were made in 1870, both as France stopped the building of new major fortifications and photographic technology replaced the need for these labor-intensive creations. The collection was declared a historical monument in 1927 and officially established as a museum in 1943. About 100 models are housed at the museum, with only a portion on display in a dark room at the top floor of les Invalides, and another 15 are on display at Musée des Beaux-Arts in Lille.