The town of Kanchanaburi was originally established by Rama I as a first line of defence against the Burmese, who might use the old invasion route through the Three Pagodas Pass on the Thailand - Myanmar border. It's still a popular smuggling route into Myanmar today.

During WW II, the Japanese occupation used Allied prisoners of war to build the infamous Death Railway along this same invasion route, in reverse, along the Kwae Noi River to the pass. Thousands of prisoners died as a result of brutal treatment by their captors, their experiences chronicled by Pierre Boulle in his book "The Bridge on the River Kwai" and popularised by the movie of the same name. The bridge is still there and so are the graves of the Allied soldiers.

West and north-west of Kanchanaburi city are several of Thailand's largest waterfalls and most extensive wildlife sanctuaries. Most of the province, in fact, remains sparsely populated and wild. -Lonely Planet.com