Tak is famous for the "Tee lor su" waterfall.
"Tee Lor Su" means "Black Waterfall" in the language of the local "Gaolian" hilltribes. The Tourism Authority of Thailand claims that it is one of the six best waterfalls in the world in terms of size (height) and beauty (sic). Also that it is the best in South East Asia, again in terms of size and beauty. The waterfall is famous in Thailand and almost all well educated Thai will have heard about it. Outside of Thailand it is virtually unknown.

Tee Lor Su was estimated to be 100 metres high and 500 metres across. The figure of 500 in breath does not mean a solid volume of water. Tee Lor Su is a fall of the segmented type, 500 represents the the breadth of the various cascades and plunges. (source Dr. Frank Gregory)