TREIGNY, France – Maryline Martin, like a lot of little French girls, was besotted with the Middle Ages, with castles and maidens and knights. She worked for Pier 1 Imports for a while, then came back to this part of Burgundy and thought she would grow mushrooms. She worked instead in an agency trying to find work for the jobless, but the fakery and cynicism involved outraged her, she said.

“I decided to do something for them instead, in this very small part of the world,” Martin said.

So of course she decided to build a replica of a medieval chateau of the mid-13th century, using the techniques of the time: iron tools and no electricity.

In partnership with Michel Guyot, a neighbour who restored the nearby Chateau de St.-Fargeau, she bought an abandoned red sandstone quarry and the woods around it, which contained the oak trees, clay, sand and water (found, she said, by diviners) that would be needed for construction. The first stone was cut and laid in 1997, and now the shape of the castle is taking form, with its round towers, great hall and ribbed, vaulted arches.

The walls are now high enough that stones are raised using a pulley system driven by a man walking in a large wooden wheel, like a hamster in a treadmill. Plans call for a new wheel soon, in which two men can walk.

The intention of the castle, called Guedelon, is essentially academic and didactic – to try to use or recreate, as nearly as possible, the building techniques of the time, which is supposed to be 1241, in the early years of Louis IX.

The castle is meant to belong to a regional lord who sided with the crown after a failed baronial insurrection in 1226 – wealthy enough to use some cut stone, buy some spices and have a great hall, but not rich enough to have a drawbridge.

The site director, Florian Renucci, is a stonemason who worked on restoring national monuments, like the Pont Neuf in Paris. And a scientific council of advisers approves the plans and techniques.

While the castle is classified as art and not a home – so it does not have to meet modern building codes – the safety of the workers themselves is a constant issue. The directors negotiate with the local authorities and insurance companies, so that the stonemasons, for example, must wear goggles when they cut or chisel stone, and workers must wear steel-toed boots.

The scaffolding of wood is supported by ropes, and the local authorities insist that modern rope that has met standard tests be used for load-bearing supports. One building inspector wanted to ban the human treadmill, saying that “it was bad for the dignity of man, men are not animals,” but he finally came around.

While the workers make their own lumber, mortar and tiles, some big oak beams are bought in a neighbouring town, along with some commercially sawn limestone blocks, which are then carved by hand. Still, nearly all the stone is the quarry’s hard red sandstone.

Philippe Delage, 55, a stonemason, has an extravagant white beard. He came here to work in 2004, he said, “to come back to the stone.” He relies on his eyes to find fault lines and the inevitable imperfections of the human cutter.

“Working this way,” with ancient techniques, “is almost impossible,” he said. “But a good mason is a cheat. You always have to compensate for error.”

For Renucci, 44, the site director, the project was a path back to his real love, which are old stones. Even as a skilled renovator of monuments, he used modern materials – cement, metal bars, resin, electric tools, chemical cleansers.

“It felt like a ‘face lifting’ of the stone,” inauthentic and unsatisfying, he said. He came here in 1998 as a worker, to watch the project and judge it, but soon decided to commit.

“What is hardest to do is to enter the logic of the period,” said Renucci, who originally studied philosophy. “I don’t have to eat mammoth or think the world is flat to build a castle. But I have to think my way into the authenticity of the process.”

While the tavern-restaurant at the site does not carry mammoth, it does try to serve a reasonably medieval meal heavy on lamb, ham, sausage and preserved fish. There is a honey-based mead, but this being France, there is also beer, cider and vin de pays.

The castle kitchen itself is popular with visitors, overseen by Francoise de Montmollin, 62, who bakes flat bread with a flour of lentils, chickpeas and bran, makes pies with salted fish and roasts chickens on a spit with a “green sauce” cited in troubadour songs of the time.

Still, much is unclear about the period and its techniques, and not all historians think Guedelon is sufficiently accurate.

“For the public it’s an enormous success, and the pedagogic aspect is excellent,” said Jean-Jacques Schwien, who teaches medieval architecture at the University of Strasbourg. But there is not a sufficient scientific protocol to test methods, he said, and he believes the “glacis,” the sloping foundation of the castle, is too large and high. On the ground floor of the great tower, he insists, there should not be a door, because “they appeared only in the 15th century.”

These concerns do not much bother Martin or Renucci, who are not trying to explain everything and who feel that they have rediscovered much, like a decent recipe for lime-based mortar and a method for creating the vaulted ceilings of the time.

“After we built the first ribbed vault in 2002, people began to look at us with a bit of respect,” said Sarah Preston, a guide who first came here as a visitor and was captivated by the project. “It was the first ribbed vault built in 700 years.”

While plans are to finish the castle in the next 12 to 15 years, with its great hall, family quarters, grand staircase and tower of nearly 27 meters, the point of the exercise is the construction, not the conclusion.

For Martin, Guedelon has been “a delirious human adventure,” she said. “When they lay the last stone, it will be terrible, terrible.”