The cultural stronghold of Celtiberians was the northern area of the central "meseta" in the upper valleys of the Tagus and Douro east to the "Iberus" (Ebro) river, in the modern provinces of Soria, Guadalajara, Zaragoza and Teruel. There, when Greek and Roman geographers and historians encountered them, the established Celtiberians were controlled by a military aristocracy that had become a hereditary elite. The dominant tribe were the Arevaci, who dominated their neighbors from powerful strongholds at Okilis (Medinaceli) and who rallied the long Celtiberian resistance to Rome. Other Celtiberians were the Belli and Titti in the Jalón valley, and the Lusones to the east.