The European Heritage Days 2023, under the theme of «Living Heritage», will propose in the center of the beautiful medieval village of Urval, between its superbly restored church and its ordinary excep-tional oven restored for the occasion, a stone carving workshop. The latter will allow its author to present to the public sculp-tures shrouded in mystery, beauty and rarity. The polyhedron and the fractal star octahedron will be discovered: these strange and refined volumes essentially decorated the top of entrance pillars of the rich houses of the Southwest in the nineteenth century, especially in the neighboring department of Gers. The stonemasons of the time, creators of these amazing figures remain today unknown; the rarity and complex workmanship of their works suggest that they mastered the art of the line and the stone carving. We will try together, during these two days, to revive this enigmatic tradition.