The Gallic fortification of Hérisson is located in a recent territory, the Bourbonnais, whose particularity is its location astride three important Gallic cities, that of the Arvernes, the Bituriges and the Eduens. Between the Allier and the Cher, the oppidum is located in a wooded area, which corresponds to the south-eastern part of the territory of the Bituriges.

Comprising two nested enclosures with a total surface area of 73 ha, this Gallic fortress was the subject of a LIDAR survey in 2004 covering the entire fortifications.
In 1569, Nicolas de Nicolaï wrote that "ruins [...] the streets and paths of Cordes are still paved with large stones [...]". In the 19th century, the scholar Louis Batissier still described cobbled streets made of flat, wide slabs side by side. In 1988, a 5-metre wide section of the road was uncovered by amateur archaeologists. In 2003, a programmed excavation on the site’s rampart, on the remains of a monumental gateway giving access to the Gallic town, revealed walls built with cut blocks as well as a new section of paved road dated to the beginning of the 1st century BC.
Geomagnetic prospecting in the oppidum provided an opportunity to find the paved roads that had been reported for 450 years and to provide information on the possible urbanisation of the settlement. Three hectares were prospected in 2008 by the prototype developed by Geocarta within the framework of the ANR Celtocophys programme of UMR 8546 ENS-CNRS (AOrOc).