Located on a plateau overlooking Forcalquier, the Mourres form a group of rocks exposed by erosion and isolated from each other. They exhibit five different types of shapes (ripples, mounds, haystacks, cylinders, basins) resulting from their mode of formation. They all correspond to rock masses that pre-existed the erosion which released them and were built by a combination of sedimentation and biological activity. Composed of locally fossiliferous massive limestones dating from about 25 million years ago, they would have formed in a marshy environment from masses of aquatic grass beds that developed on the water surface and accumulated limestone by capturing and stabilizing it in their foliage. The induration of the rocks was favored by the photosynthetic activity of the plants.