Bangkok is located in the central part of Thailand on the low, flat plain of the Chao Phraya River, which has traditionally been the main transportation artery of the Thai nation. The city was established in 1782 by King Rama I of the Chakri Dynasty as the new capital of Thailand. The location was selected for its position which provided a natural defense from enemies and a rich supply of water. The city grew steadily in size and importance, increasing from its original 4.14 square kilometers to a modern megacity of 50 districts. Bangkok is still the growth pole of the whole kingdom. Bangkok is the cultural, educational, political and economical heart of Thailand. This very highly populated city is confronting major urban problems such as pollution and severe traffic congestion. Yet it remains the center of tourism for all of Southeast Asia, and is the important city in this region's industrial and financial sectors.