Back in Tuguegarao that afternoon, we have plenty of time to spare, and we decide to spend it in a nearby town. Specifically, we head to Peñablanca some 10 kilometers northeast of the provincial capital as the crow flies to explore a popular cave.

The Callao Cave is only one of 300 caves in the area, but is the most accessible, and hence, most known. It’s composed of seven chambers, each illuminated by sunlight that streams through the crevices of the cave’s ceiling. The interiors are composed of various limestone formations created by millions of years of geological processes, although the most famous feature is man-made – the first chamber has been made into a chapel containing two rows of pews that front an altar. The other six chambers are less iconic, but are nonetheless spectacular, perhaps even more so, with the beams of the afternoon sunlight producing an ethereal glow to the cavernous spaces.

Callao Cave is part of the Peñablanca Protected Landscape and Seascape, which covers a stretch of forest in the northern Sierra Madre mountain range and extends to the Pacific coastline. Largely undisturbed by man-made development, the park is a key biodiversity area with a large number of species of plants and threatened birds.

Callao Cave itself houses colonies of bats, which become alive as dark descends. Visitors can ride a boat on the river and watch these nocturnal creatures take flight with the sunset as the backdrop. But short on cash, we simply enjoy the cave and a glass of halo-halo by the park entrance before heading back to Tuguegarao.