Thailand is located at the center of the Indochinese Peninsula in Southeast Asia. The capital is Bangkok. The country's geography features mountainous regions in the north, where the highest peak Doi Inthanon is located, and a central plain dominated by the Chao Phraya River valley. The southern part of the country consists of the narrow Kra Isthmus that widens into the Malay Peninsula. Thailand is the only Southeast Asian nation never to have been colonized by a European power. It is world-famous for its tropical islands, such as Phuket and Koh Samui, and its limestone karsts in Phang Nga Bay. The climate is tropical and governed by monsoons.