 Its eastern boundary is the Hudson; a portion of its northern boundary is the Mohawk.The terrain of the county ranges from flat near the Hudson and Mohawk Rivers to high and hilly to the southwest, of the Helderberg Escarpment and the Helderberg Mountains.The highest point is one of several summits near Henry Hill at approximately 2,160 feet (658 m) above sea level; The lowest point is above sea level at the Hudson River's southernmost extent in the county.