Saint Paul is the largest of the Pribilof Islands and lies the farthest north. With a width of at its widest point and a length of on its longest axis (which runs from northeast to southwest), it has a total area of . Volcanic in origin, Saint Paul features a number of cinder cones and volcanic craters in its interior. The highest of these, Rush Hill, rises to on the island's western shore, though most of the upland areas average less than in elevation. Most of the island is a low-lying mix of rocky plateaus and valleys, with some of the valleys holding freshwater ponds. Much of its of shoreline is rugged and rocky, rising to sheer cliffs at several headlands, though long sandy beaches backed by shifting sand dunes flank a number of shallow bays.