CAPAS, PHILIPPINES -- Hell's mouth has become heavenly over the last 20 years.
When Mount Pinatubo erupted in June 1991, it spewed out more than 5 cubic kilometers, or 1.2 cubic miles, of magma and sent an ash cloud 35 kilometers, or 22 miles, into the air. It was the second largest eruption of the 20th century, exceeded only by the 1912 eruption of Mount Novarupta in Alaska.
Today, more than 3,000 tourists a month climb the volcano, whether to swim in its gemlike caldera lake or simply enjoy its beauty.
The historic town of Capas, in Tarlac Province, around 100 kilometers from Manila, is Pinatubo's best-known gateway. (Pinatubo also is accessible from two other provinces, but the Zambales route takes 16 hours and the Pampanga trail does not reach the lakefront.)
"Pinatubo is part of our history. People should explore and experience the beauty," said Mailyn Dizon of the Capas Municipal Tourism office.
From the Santa Juliana section of Capas, tourists follow a 25-kilometer trail to the crater of the 1,486-meter, or 4,875-foot, high volcano. When tours began in 1999, a ride in a jeepney, the army-jeep-turned-minibus that is ubiquitous in the Philippines, was followed by a six-hour hike to the summit.
Now, four-wheel-drive vehicles can navigate about 16 kilometers of the terrain -- reducing the effort to an hour-long ride and a two-hour hike, which can be arranged through travel agencies or directly with a local association of four-wheel-drive operators.
After hikers register at the tourism office's branch in Santa Juliana, their vehicle travels through a military checkpoint at the entrance to Crow Valley, formerly used by the U.S. Air Force as a target and bombing range. U.S. and Philippine soldiers still use the area periodically; when they do, tour vehicles are allowed to cross the valley only before 8 a.m. and after 5 p.m.
Crow Valley looks like a moonscape, its surface encrusted with lahar, a concrete-like sludge of pyroclastic deposits and water. The tracks of the tour vehicles' tires and the roaming cattle and carabaos, a local domesticated water buffalo, cross and recross each other on the parched bed of the O'Donnell River, which runs the length of the valley.
Along the way, travelers may catch sight of the San Marcos and Tambo lakes, both created by the volcano's eruption. During the rainy season, in July and August, the river and lakes can swell with little warning, so the tours are suspended.
"This trail is not permanent. Water always changes the course," said Jay-ar Rodriguez, the tour guide on this particular trip.
Water has quarried the thick lahar into lofty cliffs and small plateaus in many places. And the trail gets rougher the closer it gets to Pinatubo, so the tour driver eventually parked on the last piece of navigable flatland.
As hikers start toward the "Old Way," a gully that leads up to the crater, volcanic rocks called dacites and andesites dot the landscape. Mr. Rodriguez calls them "batong buhay," or "living rocks," because they seem to grow larger as the nine-kilometer trail approaches its destination. Actual living things are seldom seen; on this day, hikers see only a herd of goats.
At some points in the gully, the shallow streams that form the headwaters of the O'Donnell sometimes reduce the trail to a pair of footpaths, each barely a meter wide. Some rivulets of warm water are green with algae; others look like they carry animal droppings that are in fact chromite from the volcano.
Five kilometers along is a rudimentary rest stop, a thatch-roofed shed and outhouse that are the remnants of a Korean company's tourist effort called Skyway, destroyed by typhoons in 2009 and never repaired because of environmental and safety concerns.
Ahead, a wooden sign challenges hikers to complete the final distance in 20 minutes -- or be labeled "senior citizens." Beyond the sign, the path turns into an ankle-deep, tadpole-filled brook flowing into a hardy forest. Strange plants thrive here, including a tree with poisonous fruit that looks like the atis, or sugar apples, sold in local markets.
Finally, the trail ends at about 50 concrete steps and the first view of Lake Pinatubo. Called Lawa ni Apo Malyari by the Aetas, the area's aboriginal settlers, the lake is a turquoise expanse surrounded by high, uneven cliffs.
The beauty belies the volcano's destruction. In 1991 alone, the eruption was blamed for the deaths of at least 250 people and for 10.1 billion Philippine pesos, or $245 million, in damage to crops, infrastructure and properties. The blast led to the permanent closure of Clark Air Base, a U.S. military installation, and devastated a 400-square-kilometer area. A typhoon that coincided with the eruption lent an apocalyptic feel to the events; rain-fed gushes of lahar inundated towns as red lightning streaked across the sky. Globally, the volcano's output of ash and sulfur dioxide dragged temperatures down by 0.5 degrees Celsius (0.9 degrees Fahrenheit) for two years and, scientists say, hastened ozone depletion.
In a way, those doomsday details draw tourists today.
"I'm a fan of volcanoes. It's my first opportunity to see the crater after the eruption," said Wolfgang Buck, 49, a banker and hiking enthusiast from Germany. "It's my first time to see such a beautiful caldera. I didn't know there was so much water inside."
From the viewing deck, a 170-step staircase descends to the white-sand beach. While too sulfuric for aquatic life, the lake's cool, opaque waters are safe for swimming. Guides do warn that the lakebed drops off quickly and that the crater's atmosphere is erratic, turning nippy at a mere drizzle.
"The thing is, we're in a volcano, and that's quite amazing. Years ago, it was just like any other mountain," said Emmanuel Bernard, a 30-year-old accountant who was at the caldera with friends from France and Austria.
The lake, which is 2.5 kilometers in diameter, is around 85 meters deep, according to the Philippine Institute of Volcanology and Seismology. It had threatened to spill over the caldera's rim until the institute undammed the waters in 2001 by digging a trench toward Zambales.
Pinatubo's fire still manifests itself on the lake's far shore. When guides shout "bangka," the word for boat, boatmen who have been congregating in some open-air sheds respond. For 350 pesos, they will row tourists to the lake's misty Pampanga side, where the water bubbles, and the sand is so hot that locals claim it will hard-boil eggs. The only other amenities are refreshments that some people carry to the crater in ice-filled polystyrene boxes to sell at a high markup.
Retracing the hike is fairly easy, although climbing from the shore back up the 170 steps can be exhausting. Visitors who have made arrangements in advance at the tourism office may be allowed to stay behind and camp in the crater.
Tourists can also stop in Crow Valley 400 meters from the trail head at Tarukan village, home to a community of Christianized Aetas.
The Capas National Shrine, the World War II site where the Japanese herded survivors of the Bataan Death March, is in the Cristo Rey section of Capas, about 16 kilometers from Santa Juliana. A 70-meter obelisk marks the site, which is open daily and charges 10 pesos.
Mount Pinatubo's history stretches far back in time. It is known to have had at least six eruptions, with the penultimate one occurring almost 500 years ago.
But Maria Antonia Bornas, the institute's chief of volcano monitoring and eruption prediction, speculated that it could have been much more active. "It's possible that other explosive eruptions of Pinatubo vanished from geologic record," she said.
"Based on the foregoing, we'll not say with 100 percent certainty that Pinatubo would not erupt in the next few years. We never say no anymore in volcanology."
The institute, however, now ranks Pinatubo at its lowest alert level. And Ms. Bornas emphasized that it is the type of volcano that shows warning signs.
"So far, we do not see any reason, as of now, for it to reactivate next year at least," she said.
Several travel agencies arrange Pinatubo tours from Manila that include transfers to and from Capas.
Buses from Metro Manila pass Capas on their way to Baguio, Dagupan or Lingayen, and also are available in Cubao, Quezon City. Fares range from 170 to 180 pesos.
Once in Capas, a tricycle taxi can be hired for 300 pesos at the junction of MacArthur Highway and Santo Domingo 1 Road or outside the public market at Tizon Drive to reach the Santa Juliana tourism office.
One of the four-wheel-drive tour vehicles can accommodate as many as five hikers, who may split the 3,000-peso rental fee. Every group must be accompanied by a tourism office-vetted guide, who charges 500 pesos. The tourist office also charges each person 300 pesos for environmental conservation, and offers for 200 pesos a packed lunch that includes a small bottle of water. The tourism office, +63-947-391-2134 or +63-45-925-0112, has details.
Wendell Mercado of the Four Wheelers Club in Capas also arranges tours and offers bed and breakfast for 500 pesos a night. +63-919-608-4313.
This article originally appeared in The New York Times.