Thailand's capital and most populous city, Bangkok, is the country's capital and most populous city. Krung Thep Maha Nakhon, or simply Krung Thep, is the name of the city in Thai. With a surface area of 1,568.7 square kilometres (605.7 square miles), the city is located in the Chao Phraya River delta in central Thailand, and it is expected to have a population of 10.539 million people by 2020, accounting for 15.3 percent of the country's total population. At the time of the 2010 census, more than fourteen million people (22.2 percent) lived within the surrounding Bangkok Metropolitan Region, making Bangkok an extreme primate city that dwarfs Thailand's other urban centres in terms of both size and importance to the national economy, according to the United Nations Development Programme.
Due to the city's fast development and lack of urban planning, the cityscape is chaotic, and the infrastructure is in poor condition. Despite the presence of a comprehensive expressway system, an insufficient road network and widespread private automobile use have resulted in chronic and debilitating traffic congestion, which has contributed to significant air pollution since the 1990s. Since then, the city has resorted to public transportation in an effort to address the problem, running five rapid transit lines and constructing more public transportation, although traffic congestion continues to be a major concern. Long-term environmental concerns such as sea level rise as a result of climate change are a concern for the city.