The son of Constantine was T'oros I, who succeeded him in around 1100. During his rule, he faced both Byzantines and Seljuks, and expanded the Rubenid domain. Toros ruled from the fortresses of Vahka and Pardzepert (today Andırın in Turkey). Encouraged by Tancred, Prince of Antioch, Toros followed the course of the Pyramus River (today the river Ceyhan in Turkey), and seized the strongholds of Anazarbus and Sis (ancient city). Toros extensively rebuilt the fortifications at both fortresses with tall circuit walls and massive round towers. He transferred the Cilician capital from Tarsus to Sis after having eliminated the small Byzantine garrison stationed there.