Château de Guédelon aims to recreate a 13th-century medieval castle—by using technology, tools and building techniques exclusively from that era, 800 years ago.

Begun in 1997 by owners Michel Guyot and Maryline Martin in Treigny, in the Burgundy region of France, the project dedicated its first year to making tools, baskets, pots and stones. Just 35 artisans—including blacksmiths, carpenters, masons, weavers and carters with horses—have been working to create the castle; they’re limited to materials found in or around the building site, which include sandstone, wood, iron and limestone.

Guedelon Castle is an active tourist attraction, drawing more than 300,000 people per year. It’s due to be completed in 2023.