The Chateau de Guedelon was started in 1998, after local landowner Michel Guyot wondered whether it would be possible to build a castle from scratch, using only contemporary tools and materials.
Today, the walls are rising gradually from the red Burgundy clay. The great hall is almost finished, with only part of the roof remaining, while the main tower edges past the 15m (50ft) mark.
Builders use sandstone quarried from the very ground from which the castle is emerging.
Modern cement did not exist in the 13th Century, so mortar is made from slaked lime and sand. For tools they have basic ironware.