this place is the beautiful and magical "underground river". it is now one of the 28 finalists for the next 7 wonders of the world.
what's so interesting is not just the boat ride underneath a mountain but also the various and amazing images created by stalactites and stalagmites. Cove dwelling faunas also dwell in the underground rivers and are eye catchers as well. The underground river is an excellent scenic spot to visit.
for more details, you can visit the links below.