In the winter of 53/52 BC, Vercingetorix created alliances with all the Celtic tribes surrounding him by holding as hostages daughters or sons of the kings of each tribe. With this threat, he gained their guarantees of faithfulness and alliance. Based on reports in 2007 of excavations by archaeologists (radio programme of Yves Calvi with researchers in October 2007), the capital of the Arverni is believed to have been situated between Gergovie, Corent, Aulnat and several other significant areas within a 35 km range. Researchers estimate a population of 150,000 inhabitants living in the centre of this area, and a total of more than 400,000 inhabitants living in the region of these towns.