My wife and I went to southern France, stayed in Avignon for two days and seen the following:
About 15 miles north is Vaison-la-Romaine, an Oppidum, in the 4th C BC it was a Celtic capital, then a leading Roman metropolis. It has Celtic ruins as well as Roman, it is called the Pompeii of Gaul. Today it is just a great place to visit, not too large of a place.
25 miles south is Aix en Provence, about 2 miles from the center is Entremont, an Oppidum, (6th C BC) it lies on top of a hill overlooking the city. It has the remains of a Celtic village, but it's real importance is that is was a Celtic Sanctuarie. It was defeated by the Romans. In the museum called Granit are most of the finds from Entremont. It has some columns with places for the heads of their enemy. It also has a good collection of pots, tools, and stone figures (always with a hand holding someone's head).
10 miles south of Avignon is Saint-Remy. On the outskirts is Glanum, (6th C BC) It was first settled by Celts, absorbed into a Greek trading colony and then transformed into a Roman city. It is a very impressive place, with ancient sacred places of worship. At one end of the city is were the people lived and worked, and the other is the scared places.
We then traveled to the foot of the Pyrenees, on the way there we visited another celtic site, Oppidum d'Enserune. It is by Beziers. People have been living on this hill since the 6th C BC. It has holes dug into the rock where they placed their huge urns for storing food.
We stayed in Carcassonne, it was an Oppidum, then the Romans made it into a fortified town. It was never destroyed, continued to be built on and today is a charming medieval village with a wall around it. Nearby we visited a Dolman, it is a burial place for prehistoric VIP's. It was in the process's of being restored, as it had been in disrepair for many years. It was dated at 3000 years before Christ.
Last but not lest we visited Vix, by Chatillon-sur-Seine. Vix was an Oppidum, that now has nothing there, but mounds from the excavations. At the foot of the Oppidum in 1954 a grave was excavated. In it was found a Celtic princess. All the artifacts found can be seen in the museum in Chatillon. Very impressive. They have made a reproduction of the grave just as she was found. She was buried during the La Tene period about 350 BC. This was the best of all the museums we had seen.
Some thoughts on these things. The Dolman had huge slabs of stone for walls with another huge slab of stone on top. It was about 8' wide and 25' long with an earth covering. It had been robbed long ago. The princess was found in a cavity that had been dug about 15' deep, (She was placed on a wagon with the wheels removed, there were ornaments and vases placed at her side and a huge copper urn was placed near her), huge timbers had been stacked on top of each other for walls and a huge slab of stone placed on top, then covered over with earth. The wood had rotted and the huge stone had settled on top of her. She was damaged, but the robbers hadn't got to her. I see a similarity in the way the grave was laid out between the Dolman and her grave.
On the mount where the Oppidum had been, a 12 century church was built. It is all that is there now. the village of Vix is at the foot of the hill, I think the people believe it is a sacred place.
Doug