In older geographers, the term Cantabria referred to an expansive country bounded by the Cantabrian Sea (the Bay of Biscay), the western side of the Sella valley in Asturias, the hillfort of Peña Amaya in Burgos, and along the Aguera River almost as far as Castro Urdiales. It thus included areas of Asturias, Santander, Biscay, and Guipuzcoa. Following the Roman conquest of Spain, however, it was restricted to the area of Santander and eastern Asturias, forming a part of Hispania Tarraconensis ("Tarragonan Spain"). The principal tribes of the area were the Pleutauri, the Varduli, the Autrigones, the Tuisi, and the Conisci or Concaui, who were known for feeding on their horses' blood. The area was well settled, with the largest city being Juliobriga, and the local mountains exploited for lead mines.