sentences:  While US 11 runs across the base of a valley flanking the river, the freeway proceeds along the valley's eastern edge, overlooking the valley road on its way to the Broome–Cortland county line.Both routes cross the border at points just yards apart, beginning their transition from the Southern Tier region to Central New York.About from the county line, I-81 encounters the village of Marathon, situated inside the river valley at the junction of US 11 and NY 221.