Timeline

Heritage classified

Key figures

Origin and history

The ancient ironworks in Tannerre-en-Puisaye are one of the two largest steelworks in France, with iron extraction residues dating back to the Gaulish era. Located in and around the Bois de la Garenne, it covers 30 hectares, of which 15.2 ha have been listed as a historical monument since 1982. This site, operated by the Senons from the 7th century BC, reached its peak under the Roman Empire, with an estimated production of 80% of the total over 300 years. Gallo-Roman techniques produced slags comparable to modern blast furnaces.

Activity declines in the High Middle Ages, leaving room for remains like slag mounds 15 meters high. In the 10th century, the Motte Champlay, a castle keeping the road to Paris, was built there, then destroyed in 1359 by the Anglo-Navarres. The site was industrially re-used in the 20th century for its iron-rich ballast and slag (up to 70%), used in the Lorrain blast furnaces. The extraction ceased in 1982 after the site was classified.

Today, the ferrier is valued by a local association that has developed orienteering racing routes, reconstructed ancient blast furnaces and an educational train circuit on the old 19th century railway track. Guided tours and demonstrations of ore reduction are organized there, including during Heritage Days. The site, free of access, combines industrial heritage, archaeology and pedagogy, with explanatory panels and equipment such as a rest area.

Research revealed deep Gallo-Roman wells of 6 to 9 metres, pits of extraction and traces of the Champlay Motte, razed in 1360. The ores mined were mainly red hematite (70% iron) and lemonite. The ferrier, surrounded by 75 hectares of wood, illustrates the historical importance of Puisaye in ancient metallurgy, with more than 2,250 ferries listed in the region in 2008.

The association has recreated workstations showing ancient and modern techniques, including a functional furnace (800–900 °C), a medieval forge and a 19th century bellow. A historical booklet, published in 2013, documents the site. The slags, formerly exported to Lorraine, also contained silica, which was used to melt in blast furnaces. Ferrier remains a major testimony of Gallic and Roman metallurgical innovation.

Future

The industrial exploitation of the site ceased when it was classified as a historical monument in 1982.

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