A white wall, plastered and sturdy, with a peach tree trained against it: this simple image once defined the landscape of Montreuil, a commune in the Seine-Saint-Denis department near Paris. For centuries, local market gardeners cultivated peaches by training the trees against plaster walls. This technique, which began in the 17th century, became so widespread that it transformed the area into a unique network of walls, stretching over 600 kilometers—roughly the distance from Paris to Bordeaux. These walls functioned like radiators, absorbing solar energy during the day and releasing it at night, which helped protect the fruit from frost and speed up ripening. In 1870, at the height of this agricultural practice, Montreuil's walls supported the growth of 17 million peaches, a number nearly equal to the population of the Netherlands at the time. Each person in the Netherlands would have received about one peach from Montreuil’s production. These fruits were exported across France and beyond, highlighting the region’s historical significance in fruit cultivation. However, modern urbanization has drastically reduced this landscape. Today, only a small fraction—about one sixtieth—of the original network remains, with just a few kilometers of walls still standing. Efforts to preserve what remains have been limited. In 2003, a decree classified 8.5 hectares of the area as protected sites and landscapes—roughly the size of twelve football fields. While this classification offers some level of protection, local environmental groups argue it is insufficient compared to the vast areas that have disappeared. The association Environnement 93, for example, describes the measure as a "trivial patch" in the face of the extensive damage caused by urban expansion. Despite these challenges, some remnants of the peach wall tradition still exist. A photograph of a white plaster wall with a peach tree trained against it, its branches fanned out in a natural shape, captures the essence of this unique agricultural practice. These scenes can be found in small plots maintained by local associations, which also organize visits and events. The city of Montreuil has also taken steps to protect the remaining walls by designating a 28-hectare agricultural zone, where construction is restricted to ensure compatibility with the heritage of the peach walls.