 Pliny the Elder in his "Naturalis Historia", in section 24, lists the towns belonging to the Caesaraugustan Juridical Convent, among which they appear the Ercavicenses (of the city of Ercavica, neighbors of the Segobrigans).Later, in section 27, it defines Segóbriga and its area as "caput Celtiberiae" ('head of Celtiberia'), which reached to Clunia ("finis celtiberiae"), following a geographical order from the South to the North, which suggests, together with the previous data, that the Segóbriga zone was the boundary between the Celtiberians and the Carpetanis.It also indicates that Segóbriga was a stipendiary (tributary) city of that Conventus.