North and west of the capital, the unwieldy urban mass of Greater Bangkok peters out into the vast, well-watered central plains , a region that for centuries has grown the bulk of the nation's food and been a tantalizing temptation for neighbouring power-mongers. The riverside town of Kanchanaburi has long attracted visitors to the notorious Bridge over the River Kwai and is now well established as a budget-travellers' hangout. Few tourists venture further west except to travel on the Death Railway, but the tiny hilltop town of Sangkhlaburi is worth continuing for. On the plains north of Bangkok, the historic heartland of the country, the major sites are the ruined ancient cities of Ayutthaya, Lopburi and Sukhothai. Mae Sot makes a therapeutic change from ancient history and is the departure point for the rivers and waterfalls of Umpang , a remote border region that's becoming increasingly popular for trekking and rafting.