Partly volcanic and partly coral in origin, Antigua has deeply indented shores lined by reefs and shoals; there are many natural harbors and beaches. Boggy Peak (402 m/1,319 ft), in southwestern Antigua, is the nation's highest point. Antigua's northeastern coastline is dotted by numerous tiny islets; the central area is a fertile plain. Barbuda, a coral island with a large harbor on the west side, rises to only 44 m (144 ft) at its highest point. Redonda is a low-lying rocky islet.