Puerto Princesa Underground River Day is observed in the Philippines every November 11 to celebrate the Puerto Princesa Subterranean River National Park (PPSRNP), which was voted one of the New 7 Wonders of Nature in 2011. The park, located on the island of Palawan, features a remarkable limestone karst landscape and a 5.1-mile-long underground river that flows directly into the sea. It serves as a significant habitat for biodiversity, hosting over 800 plant species, 165 bird species, and various mammals and reptiles, including many endemics. Established as a UNESCO World Heritage Site in 1999, the park has been managed by the local city government since 1992. The day was officially declared in 2014 by the Philippine president to commemorate its recognition as a natural wonder. On this occasion, the park administration organizes educational and entertaining events to highlight the importance of biodiversity and nature conservation. Visitors are encouraged to explore the park's landscapes and participate in activities that promote environmental awareness.