Mecca, the best-known Arabic word in English, is more than an advertising slogan, as in "tourist Mecca." Mecca is a modern mountain city of 1 million people in western Saudi Arabia. Because only Muslins go there, outsiders don't know much about it.

Yet once a year, for a few short weeks, Mecca attracts more visitors than almost any spot on Earth. I'm heading there this evening as the sun sets over the Red Sea, flying on a jumbo jet with hundreds of other pilgrims, on my way to perform the hajj, or pilgrimage. Today most visitors arrive by air. In other ways, however, this is a journey into the past. Mecca, the birthplace of Islam, is steeped in history and legend We are going back into the past for a few days, to recover some of our own original spirit, by walking in the paths of Adam and Eve, Abraham and Hagar, and the millions of pilgrims who have come here before us.

Leaving the airport, our bus climbs treeless mountains for an hour. We're dressed in timeless-looking garments; the women in simple robes of black or white, the men reduced to two lengths of unstitched cotton. It's hard to tell a sweeper from a prince. We take a vow as we don these clothes to regard Mecca as a sanctuary and to treat other pilgrims gently, with respect.

We leave more than fashion at the border. In some indescribable way we leave ourselves.

As the bus winds through town, I'm sitting next to a Bosnian student named Ali. "Sure, you have to be careful," he says. "Yes, the crowds are enormous. But look more closely. It's not your normal crowd." A glance out the window confirms this. Streams of men and women from 125 nations fill the sidewalks and streets. Yet no one is pushing. Everyone is flowing-a slow crowd, a patient crow. "You just have to get into the swim of it," he says. "The best place to do that is in the mosque."

Mecca's mosque is hard to miss. Its coliseum-size walls and bright, moon-rocket minarets tower above the streets from blocks away.

This vast temple complex can hold a million people. Most pilgrims arriving in Mecca come straight here. Even at midnight the mosque is in full swing. A hundred thousand people fill the ground floor colonnades. It takes me 15 minutes to pass from the outer gates to the core of the complex, where a white marble floor gleams under stadium lighting like an ice rink. This part of the mosque is open to the stars.

Here, I join a ring of 5,000 people surrounding a small, stone building draped in black: the Ka'bah, a windowless structure with simple lines that Muslims call God's first house of worship. The rest of the temple complex is a mere surrounding for this modest, ancient building. The Ka'bah marks the direction in which Muslims pray all their lives. Seeing it for the first time brings smiles and even tears to people's faces.

The human ring around the Ka'bah is moving counter-clockwise in a circuit called the Turning, a special form of walking prayer. Around we go seven times at a stately pace, while the still point of the Ka'bah towers above us. The movement of so many people in one direction sets up a soft, pervasive whisper on the floor, of clothes brushing skin, of bare feet over marble. The Turning continues day and night, with every pilgrim making seven rounds. Viewed from above, the people and building form a single figure--of God's House at the center of their lives.

My turns complete, I descend a nearby stair to the Well. It is cool and dim down here, with a pumping station and several hundred basins. This is the well without which Mecca would never have existed. (It is mentioned in the biblical Book of Genesis.) Like everybody else, I take a sip, then return upstairs to the last rite of the evening: a ritual jog between two hills on the far side of the mosque. As I move along, I remember the sweet tasting water. That's how it is in Mecca. You become a vessel into which timeless meanings are being poured.