[4] Metal extraction also requires a lot of water to wash the ore,[5] a need fulfilled with the Branlin river flowing at the foot of the hill.

[6] Lastly, extracting iron required air to activate the bloomeries and the site is at the top of a hill, well exposed to winds.

Surface ore eventually became all used up, so mining holes were dug down to 2 m (6.6 ft) deep;[5] many examples of that operation remain within and around the ferrier, generally partly refilled and often retaining water.

This place is less than 40 km (25 mi) (on a beeline) from the Loire river and from the Bituriges, to whom is attributed the discovery of tinning and who were held among the best regarding their metalwork in general and ironwork in particular.

[8][11] The oldest bloomeries studied in France, some "trapped slag" furnaces (fours à scories piégées) giving off only a low production, are in the area of Sens only 50 miles away to the north and may date from the 7th century BC.

[7] Already largely present in Celtic times, (the Iron Age in western Europe started around 800 to 700 BC), the site's production tremendously increased with the Romans intent on grabbing resources in conquered territories.

The means and techniques that they put to use produced what is called in French « scories à laitier » literally « milk slag »[note 3] of the same quality than those of modern blast furnaces.

[9] It was taken over in 1359 by the English captain Robert Knolles, in the service of Charles II of Navarre during the latter's attempt to take over the French crown.

From 1900 to 1982 the ferriers' mounds were used on industrial scale, systematising the use (a trend already started in the 19th century) of slag to "iron-load" the roads and for rail track ballast.

[10] During those times a complete network of railway tracks covered the ferrier along with switches, turntables, derailers, workshop and well.

Using these considerably modified the ferrier in many ways, notably by greatly upsetting the order of archaeological strata in many places and thus locally preventing near-any historical tracing.

This new exploitation stopped when the ferrier was classified as monument historique in 1982,[12] leaving for the future researchers a vast land open for investigation; it has been so disturbed that Henri de Raincourt, the minister present at the inauguration in September 2009, compares it to Verdun or the ligne Maginot.

[10] After the land was abandoned for 20 years, the "association du ferrier de Tannerre", created in 2008, did a lot of work to make the site known to the public.

[9] A thorough research allowed to identify the Motte Champlay fort, le railway tracks, sites of activity at the beginning of the 20th century and other interesting points.

[10] La communauté de communes a misé on the creation of orienteering courses, this being facilitated by that the wood is not a hunting ground: it can therefore be open to the public all year round.

The first two events in June 2011 and March 2012 were the final tests for the new courses before the National association for school sports (in French Union nationale du sport scolaire or UNSS) Academy championship on April 17, 2012, with 177 runners who expressed unanimous appreciation for the new courses and have helped strengthen the reputation of the grounds' installations.

[10] The ferrier association has also re-created some workstations showing the successive stages of ore extraction and processing during Antiquity and during the last two centuries.

[12] It asked for help from the association "Le Petit Train de Champignelles",[22] which provided needed documentation and support.

These efforts have brought to life a site that is representative of the ferrier exploitation during the 19th century, with discovery paths that link all the main history points.

[10] Guided tours and demonstrations of direct iron reduction in bloomeries are organised yearly, usually during the ferrier feast beginning of September and the Heritage Days later in the same month.