Mt Pinatubo is 50–60km east — one of the most dramatic day trips in Luzon. The 1991 eruption was the second-largest of the 20th century and left a crater lake of striking turquoise. The hike to the crater (typically via a 4WD transfer to the trailhead) takes around 2 hours each way and is well worth the effort.
Pundaquit and San Antonio, south of Olongapo, are quieter fishing villages with access to diving, surfing, and offshore islands including Capones Island and its lighthouse. Significantly less developed than the Subic Bay freeport.
Bataan Peninsula, across the bay, requires a ferry crossing but offers historic WWII sites including the Death March memorials and Mt Samat with its giant cross visible from Subic Bay.