Cambodia's main geographical features are the low lying Central Plain that includes the Tonlé Sap basin, the lower Mekong River flood-plains and the Bassac River plain surrounded by mountain ranges to the north, east, in the south-west and south. The central lowlands extend into Vietnam to the south-east. The south and south-west of the country constitute a long coast at the Gulf of Thailand, characterized by sizable mangrove marshes, peninsulas, sandy beaches and headlands and bays. Cambodia's territorial waters account for over 50 islands. The highest peak is Phnom Aural, sitting above sea level.