There are several mountain regions in the country, the Dangrek Mountains in the north and the Cardamom and the Elephant Mountains in the south. In addition to these mountain regions the country mainly subsists of lowland regions with fields and green forests. Cambodia also possesses the largest lake in South East Asia. This lake is the Tonlé Sap, or the Great Lake, which connect with the Mekong River. The lake increases its size up to four times when the water rises during the rainy season from the end of May to October. This season is also the reason for the river Tonlé Sap to flow northward into the lake Tonlé Sap. However, during the dry season it reverses its flow and flows back to the Mekong River in the south. As a result of this, the lake Tonlé Sap has become a great resource for freshwater fish and thus one the richest sources in the world. There are two monsoon seasons in Cambodia; the cool north-eastern monsoon that is rather dry and lasts between November and early May, and the wet south-western monsoon which brings heavy rain, strong wind and high humidity from the end of May to early October. For the international traveler the country has to offer small picturesque villages situated along the dirt roads, lively cities as Phnom Penh and Battambang, smaller towns such as Siem Reap and of course the town of Sihanoukville that is situated along the beautiful coastal strip by the gulf of Thailand.