A ROCK ALTAR in a cold cavern. A Nativity scene formed out of natural stone formations. The face of Jesus engraved by time onto a limestone wall. Healing waters flowing from the heart of a sacred mountain.

Most would immediately think about Mt. Banahaw, but few know that there is another mountain closer to Manila which holds powers of healing.

As in Mt. Banahaw, faith and superstition intertwine in Nelly Deles-Natal's Mystical Cave, located about 16 kilometers from Quezon City, or about half an hour's drive away on a Sunday.

Nelly was born in Iloilo in 1943. At the tender age of seven, she began having prophetic dreams.

''At first she only dreamed of a mountain that she will eventually go to,'' said Joy Natal, Nelly's daughter-in-law and one of the caretakers of the cave.

''But when she turned 10, the voice of God the Father began speaking in her dreams, and it told her she was meant to take care of that special place.''

Nine years later, Nelly started what she calls ''divine healing,'' which is similar to what is popularly known as faith healing.

In 1970, Nelly traveled to Manila. She found the place she had seen in her dreams in Barrio San Isidro, Antipolo, Rizal. She bought the 496-hectare land, on which stands the mountain with the mystical cave, for roughly P2.5 million.

''At first, only a small portion of the cave could be seen,'' recalls Nelly's youngest son, Christopher. ''Then they used dynamite to carve out an entrance big enough for people to pass through.''

Christopher said the natural images in the cave were discovered by visitors in the early 1980s. Formed by water dripping into the cave and enhanced by the play of light and shadow, the images are predominantly of Christian influence.

Visitors, mostly foreigners, come to the cave either to be healed of physical ailments or for evil spirits to be cast out of their bodies.

''They actually see the caves in their dreams, and are moved to tears in knowing intuitively that they found what God had wanted them to find,'' Joy said.

''When Nanay (Mother) Nelly sees them, she instantly knows their past, their future, and what kind of healing they need in the present.''

Today, to fully experience the magic in the Mystical Cave, it is essential to visit the many images.

Some famous examples are the Bethlehem scene made of stalagmites the size of one's hand; the image of the Pieta formed on a limestone wall by patterns of seeping water; and the hand of Christ made of stalagmite ''fingers,'' with a hole in the middle of the palm.

Other images include Noah's ark, the eagle and sheep (symbolizing pride and humility), the wedding bell, and a wishing heart for lovers.

There is as well a limestone bathtub, which also has healing properties.

The ''architect'' of the place must have a lot of foresight because close by is a ''dressing room,'' again made of natural limestone configurations.

To get to the cave, we experienced a moderately difficult ordeal, making the trip some sort of a pilgrimage.

First we climbed 150 cemented steps, passing what they call a Wishing Rock halfway to the top. There, we lighted a candle--one among many sold in the vicinity--and secretly, whispered our hearts' desires.

Along the way, we saw many animals and insects--dogs, turkeys and geese, and thousands of ants which accompanied us at intervals on the way up.

At the top of the stairs hung an abundance of signs indicating the use and potency of bloodstones (for sale to interested parties).

Joy told us the story of the stones: ''Nanay Nelly received a message in her dreams that she was to propagate the use of bloodstones for healing. These stones were at the foot of Jesus' cross and received the gift of His blood as it flowed from his wounds.

''After immersing a stone in water for 15 minutes, one should drink the water. Different sicknesses will be cured. For good luck in business, you should put it in the cash register; for safety in traveling, put it in your car; for personal safety, carry it in your pocket.''

Joy said that only Nelly knew where the stones could be found in the Philippines, and that one would have to pass through a forest filled with snakes to get there.

We bought some roughly cut stones for P30 apiece, shying away from the finished and polished ones with prices ranging from P300 to P1,200.

Yet another thing caught our attention: another flight of cemented steps leading higher up into the mountain. The sign read ''The Way of the Cross.''

After some debate, we decided to give it a try. We were told that it would take around 20 minutes to get to the top.

To our dismay, after a short flight of steps, the path disintegrated into an upward slope of slippery clay, sharp rocks, and thorny trees.

We abandoned our pilgrimage, agreeing among ourselves to atone for our sins in another way, or to come back and try again in more appropriate clothes and shoes.

For many, the cave obviously has a religious purpose. It now has its own following among the young and old--the sick looking for a way to heal themselves, foreigners seeking adventure or a place revealed in their dreams, young students drawn by curiosity, environmentalists and children.

Yet the Mystical Cave is clearly not at the same level of popularity as Mt. Banahaw. But perhaps this is an advantage--a way to keep its natural environment clean.

''We don't promote the cave,'' Joy told us. ''People just come on their own free will. But we have been featured in the media, like Sky Cable.''

On the first level of the seven-floor cave is a cathedral-like site. In 1982, Bishop Teodoro A. Salcedo, D.D. of the Holy International Church celebrated Mass there--a first in the Philippines. In 1989, the first cave wedding was performed, joining Vicente Cañozo and Florida Floriendo in holy matrimony. Some scenes from ''TGIS,'' the movie, were shot in other parts of the cave.

But most flock to the cave in the hope of getting healed of their ailments. Parents bearing infants as young as six months old go to bathe their children in the waters.

Nelly claims that a variety of diseases can be cured after two or three visits to the cave. No medicines are prescribed, only prayers, especially the recitation of the rosary, some herbs, and meditation. Asthmatic people have to spend the night in the cave to get cured.

The character of the Filipino is basically superstitious.

''According to the Catholic Church, the danger lies in the assigning of divine powers to physical objects,'' said Fr. Adolfo Dacanay, S.J., director of the Institute of Canon Law of the Loyola School of Theology, in an interview.

The Filipino is also very religious, and it is through this combined faith that he visits places such as the Mystical Cave or Mt. Banahaw to heal himself, not only in the physical sense but also psychologically and emotionally.

''Healing is a matter which deals with questions of facts,'' Dacanay added. ''If a person gets cured, and it can't be medically explained, then just accept it as such. And if you believe in God, then ultimately. you'll believe that it's an act of God.''

What makes the cave so mystical? Is it the fact that the natural formations coincidentally symbolize our Catholic faith? Is it the pre-Hispanic belief that spirits inhabit plants, trees, and, yes, even rocks, mixed with the more modern Catholicism? Is it our inculturated Christianity, our unique brand of ''bastardized belief?''

Or is it the fact that the waters that run underneath and within the cave have actually healed people?

Whatever the answer, Nelly Deles' Mystical Cave will always attract those with faith or adventure in their hearts.