The Coiano fulling mill, an ancient factory of medieval origin, has defied the passage of time and gone through numerous transformations during its long history in the art of wool processing.

From these structures was born the tradition of carded textiles, an excellence of the Prato district. Since the late Middle Ages, a complex network of water channels, known as "gore", has made the creation of these productive factories possible. Despite the passing of the years, the interior of the building still retains the essence of the past, with the machines revealing the secrets of the ancient production process.

The Coiano fulling mill represents a precious example of industrial archeology in Prato, maintaining intact the complete structure of the hydraulic artefacts (millpond, margone and supply outlets) and of the production process, with machinery, pulleys and transmission shafts. These machines were driven by two hydraulic turbines, powered by the powerful current of the Bisenzio river thanks to a complex water canalization system, which involved the millponds and the Cavalciotto, a complex water diversion structure on the Bisenzio. In the fulling mills, hydraulic energy set in motion the log frames, a kind of hammers, which crushed the rags or animal fibers, in a process called "fulling", which gave the fabric greater compactness and impermeability. The wool was then treated with a special clay called "terra follona", known for its felting properties, and this clay was extracted from Monte Ferrato, in the Galceti area, from which the name of the place seems to derive. Thanks to this technique, Prato's wool workers specialized in the textile activities that still characterize the area today.

The first evidence of the Coiano fulling mill dates back to the 12th century, around 1180, when it was a mill owned by the parish church of Santo Stefano of Prato. After, it passed to the Naldini family who converted it into a fulling mill. Until a few decades ago, the Coiano fulling mill was still in full activity, but in the 1990s it ceased its operations. However, the building still retains its fascinating production structure intact, with the machines that bear witness to the industrial archeology of Prato. Today, under the care of the Municipality, which has become its owner, the Fulling mill is ready to be reborn thanks to a careful restoration.