Alta River is a small river in Ukraine and is a right tributary of the Trubizh. The ancient town of Pereiaslav is situated between the Trubizh and Alta rivers. The river is considered the place where the assassins sent by Sviatopolk the Accursed killed saints Boris and Gleb in 1015. In 1019 it was the site of a battle between Svyatopolk and his brother Yaroslav …Alta River is a small river in Ukraine and is a right tributary of the Trubizh. The ancient town of Pereiaslav is situated between the Trubizh and Alta rivers. The river is considered the place where the assassins sent by Sviatopolk the Accursed killed saints Boris and Gleb in 1015. In 1019 it was the site of a battle between Svyatopolk and his brother Yaroslav I the Wise which Yaroslav won.