Pinayungan Cave is located in Pili, San Marcelino, Zambales, Philippines.

A rare oppurtunity to trailblaze the path covered by the volcanic eruption as one visits a community in San Marcelino town now transformed into a lake-all caused by lahar situation of river channels. Take a boat ride and see more than 600 houses, schools and churches permanently submerged in a huge body of water. From the high trail, one may get a close-up view of the volcano. On one's way back, a visit to a prayer mountain called hidden shrine of Mt. Pinatubo is recommended.

Source:

Angelfire.com