island and city, southern Philippines, in the Celebes Sea. Basilan island lies 5 miles (8 km) off the southern tip of the Zamboanga Peninsula of Mindanao, across the Basilan Strait. It is the largest and northernmost island of the Sulu Archipelago. Most of the island consists of rugged or rolling forested uplands, with several volcanic peaks exceeding heights of 2,000 feet (600 m). Short streams provide a roughly radial pattern of drainage. Since about 1900, lumber mills have operated in the tropical rainforest. The island's gentle, rolling slopes and its valleys have fertile soils and are largely under plantation agriculture. Rubber, the primary crop, is processed on the plantations and sold to Manila factories.
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