Château de By, Historical château in Thomery, France

Château de By is a castle in Thomery situated on a 4-hectare park beside the Fontainebleau forest, featuring a neo-Gothic studio with large windows for natural light. The museum displays Rosa Bonheur's original paint containers, work tools, personal archives, and rotating exhibitions of her animal paintings.

The château was built in the 15th century as a seigneurial residence and reconstructed in the 18th century. Rosa Bonheur bought it in 1859 and lived there until her death in 1899, keeping her studio and animal quarters on the estate. Her heirs sold the property in 1900, and it later became a museum devoted to her work.

Rosa Bonheur installed a photographic laboratory at By, where she had herself photographed in her studio and used photographs as working documents for her animal paintings. The room and its equipment survive, showing how she combined photography with drawing and painting in the second half of the 19th century.

The grounds can be explored along paved paths that lead to different parts of the park and studio. Visiting works best during opening hours when guided tours are available.

Rosa Bonheur kept a menagerie at By that grew to include lions, a yak, deer and sheep, and she obtained a permit to wear men's clothing so she could study animals at fairs and slaughterhouses. Visitors can still see the animal stalls she had built in the park.