The oppidum of "Nandin" at Château-Porcien stood on the chalk cliff fifty metres above the north bank of the Aisne and the wetter land of the river's flood plain. 

The precise Gallo-Roman organisation of the whole plateau shows two main roads meeting each other at right angles more or less at its centre. At the edge of the plateau, on its south face, a fanum has been excavated. A structure on posts and ditches filled with the bony part of ox horns, cut into by the foundations of the peribolos, are the remains of an earlier site, probably dating from the end of the Gallic period.

The many Gallic coins found there were mainly struck in bronze and part of the series bearing the inscription Atisios/Remo, probably the local chief after the Conquest. 

At the south east corner of the oppidum, at "La Briqueterie", a cemetery was destroyed by the extraction of soil for brickmaking. Among the Gallo-Roman tombs were a few elaborate cremations from the end of the Gallic period, with bronze swords and tableware, notably pitchers (Kelheim type).

A short distance away, the outline of an immense Roman temple has been observed from the air. The objects found in this sector indicate its occupation from the 1st century BC to the 4th century AD.