Zamboanga City is a highly urbanized city on Mindanao, Philippines. Zamboanga City is the 6th most populous and 3rd largest city by land area in the Philippines. It is the commercial and industrial center of the Zamboanga Peninsula Region. The southwest and eastern sides of Zamboanga City are bounded by irregular coastlines with generally rocky terrain and occasional stretches of sandy or gravelly beaches. The coastal profile usually descends abruptly towards the sea. Where rivers enter the sea, bays have formed, and the surrounding area has filled up with alluvial soils, producing small to large coastal plains. The overall topography of the city could be described as rolling to very steep. There are some flat lands, mostly narrow strips along the east coast.