Vietnam borders China in north, Lao PDR and Cambodia in west, The nation is bordering South China Sea in east, and the Gulf of Tonkin with the island of Hainan Dao (China) in north-east. The country shares maritime borders with Indonesia, Malaysia, Philippines, and Thailand. With an area of 331,689 km² Vietnam is about three times the size of Bulgaria or slightly larger than the U.S. state of New Mexico. About 40% of Vietnam's total land area consists of mountains while 42% are covered with tropical forests.