On Thursday, Pope John Paul II will begin his visit to Egypt, the highlight of which will be his pilgrimage Saturday to Mount Sinai in the south-central part of the peninsula we now call the Sinai. But is that really the mountain where Moses received the tablets of the law from God?

Of course some skeptics, including scholars, doubt that any of it ever happened. But we'll leave that to the theologians. For our purposes, it's irrelevant. For thousands of years people have believed it happened. Even today millions and millions of people believe it happened. And whoever first recorded the tradition must have had some place in mind.

Many places mentioned in the Bible have retained their identity so we can be sure where they are--Jerusalem, Bethlehem, Jericho are examples. Others we're pretty sure about--like Pithom and Ramses, the store-cities the Bible says the Israelites built in Egypt.

Some sites, however, remain a puzzle. And Mt. Sinai is surely one of them.

A few years ago, the Biblical Archaeology Review listed ten different sites scholars had proposed for the holy mountain.

The tradition that the site known as Jebel Musa in Arabic is Mount Sinai goes back only to the 4th century A.D. That's more than 1500 years after the best guess as to when Moses lived and the Exodus occurred (about 1250 B.C.).

The mountain was first identified as Mount Sinai by Christian monks in the early centuries of the monastic movement. In the 6th century A.D. the Byzantine emperor Justinian built an imposing fortress and monastery to protect the monks who were already living precariously at the foot of the mountain near a small chapel commemorating the "burning bush."

Not until the 11th century A.D. was the monastery named for St. Catherine, a Christian martyr who was beheaded by a Roman emperor and whose head and body, according to legend, were brought there by five angels.

According to Harvard professor Frank Cross, the entire notion that Mount Sinai was located in what is now called Sinai was "created for pilgrims" as far back as the 4th century A.D.--and perhaps even earlier--when Christian travelers were already visiting the site.

One difficulty in locating the mountain stems from the fact that the route the Israelites took through the Sinai is also unclear. Most scholars, however, opt for the southern route and Jebel Musa is one of the highest mountains in a rugged granite massif in this area. You might say that, given the long tradition and the likelihood of the southern route, that's enough to make the case.

Besides, Jebel Musa is clearly the most magnificent, awe-inspiring of all the candidates. Whether or not it is the real Mount Sinai, a trip there will leave you with a better understanding not only of why it may have happened there but the spiritual meaning of what happened.

More recently, scholars have put forward two other candidates based on archaeological finds. One is Har Harkom (Mount Saffron in English), a site just inside Israel on the Israel-Egypt border, where Italian archaeologist Emanuel Anati has been surveying and excavating since the 1980s.

Anati has discovered an enormous amount of rock art that identifies Har Harkom as an ancient pilgrimage site--a praying man with upraised arms, a sacred "eye of God," a grid with ten squares that may represent the Ten Commandments, and a twisting snake next to a straight line that may represent the staff that was turned into a snake.

Anati also claims to have found hundreds of campsites, sacred pillars, tombs covered with piles of stones called tumuli, and even altars. The problem is that none of this can be dated to the biblical period, even by Anati. It's all much earlier.

So far, few, if any, scholars have agreed with Anati's identification of the site as Mount Sinai.

The other candidate which has received a lot of publicity lately is in northwestern Saudi Arabia. The case for Jebel el-Lawz requires a bit of biblical background.

Moses married the daughter of Jethro, a priest of Midian. It was while he was tending Jethro's flocks that Moses first saw the "burning bush" at the foot of what would later be Mount Sinai.

So Mount Sinai must be in Midian. For a long time, the location of Midian was uncertain. But archaeology has now changed this. We know what Midianite pottery looks like. And we know that Midian was located in southern Jordan and northwestern Saudi Arabia. Moreover, unlike the Sinai which was unoccupied at the time of the Exodus, Midian has produced considerable archaeological evidence of habitation.

So that is where many scholars now believe Mount Sinai is located. Just where, however, remains a mystery.

The highest peak in the area is Jebel el-Lawz, so that remains the best, if highly speculative, candidate.

A recent book called "The Gold of Exodus," touting the adventures of two non-scholars who snuck into Saudi Arabia to examine Jebel el-Lawz, makes exciting reading, but adds nothing to the scientific case for it.

Interestingly, Jewish tradition does not locate Mount Sinai. The theophany on the mountain is frequently referred to in the Bible, yet there is never a biblical pilgrimage to the holy mountain. And even later rabbinic tradition does not identify where it is located.

Maybe we're not supposed to know. Maybe it is one of those things God intended to remain a mystery.