I was only ten years old when Mount Pinatubo erupted in a cataclysmic way on June 15, 1991. I don’t remember much about it except waking up one morning a few days later to see everything blanketed in snowy white ash. This eruption occurred barely a year after the 1990 Luzon earthquake devastated Nueva Ecija and Baguio, leading to the moniker that the 1990s was the decade of natural disasters for the the Philippines.
The Pinatubo eruption was extremely notable in many respects. It is considered by volcanologists to be the second largest volcanic eruption of the 20th century after the 1912 eruption of Novarupta in Alaska. Given the fact that Novarupta occurred in a remote unpopulated area, this makes the Pinatubo eruption the most significant geologic event of the last century, eclipsing the impact of the 1980 eruption of St. Helens in Washington.
The Pinatubo eruption is rated 6 (i.e., colossal) on the Volcanic Explosivity Index, which is the volcanic counterpart to the earthquake magnitude scale. An estimated 10 cubic kilometers of material was ejected into the atmosphere blanketing 125,000 km² of land with ashfall and indirectly killing about 700 people (mostly due to collapsed buildings sagging under the weight of the ash). It devastated Central Luzon economically and each rainy season in the following years brought lahar rampaging down the countryside. The suspended volcanic material in the atmosphere also contributed in bringing down global average temperatures by about 0.5°C and increased the destruction of the ozone layer. (But it did bring about spectacular sunsets everywhere.) Furthermore, the eruption hastened the planned abandonment of the United States bases in Clark and Subic Bay.
Today, the lahar flows have subsided and the Mount Pinatubo crater is now a lake. Tourism activities have picked up and people now regularly go to the summit via a long trek from the north (which I inferred from a tell-tale trail of geo-referenced photos in Google Earth). In fact, you can follow the trail in Google Maps. Start at this tiny hut near the crater lake and trace the narrow trail leading through the forests and lahar rivers northwards. There’s also plenty of pictures from crater hikers in Flickr, and I would really recommend that you check out the crater in Google Earth (link below)—the terrain is amazing!