Fodor's Expert Review Tham Pla-Namtok Pha Suea National Park

About 28 km (17 miles) north of Mae Hong Son on the Pai road, this park has one of the region's strangest sights—a grotto with a dark, cisternlike pool overflowing with fat mountain carp. The pool is fed by a mountain stream that is also full of thrashing fish fighting to get into the cave. Why? Nobody knows. It's a secret that draws thousands of Thai visitors a year. Some see a mystical meaning in the strange sight. The cave is a pleasant 10-minute stroll from the park's headquarters.