Located near Sebang, roughly two and a half hours from Palawan's capital Puerto Princessa, the underground river is a sight to behold. A UNESCO World Heritage site with passages totalling more than 24km, it is the longest navigable underground river in the world. Tours are available with expert local tour guides who will entertain you with stories as you explore this wonder of the world. The river is accessible all year round however it's marginally better from January to June.
Find out more here about heritage sites in the Philippines.