PPUR Day is celebrated on November 11 to honor the Puerto Princesa Underground River, a UNESCO World Heritage Site located in the Philippines. This site is renowned for its remarkable biodiversity, featuring over 230 animal species and 800 plant species, including 15 endangered bird species unique to the country. The river is notable for its "mountain to sea" ecosystem and impressive limestone karst landscape. On this day, awareness is raised about the conservation of this significant natural resource, which has attracted global interest, especially after being named one of the New Seven Wonders of Nature. Celebrations typically involve activities that promote environmental conservation and highlight the importance of preserving the unique ecosystem of the underground river.