The death of 14 Muslims made news last week when pilgrims converging on a holy site in Mecca collided with crowds leaving it. Security forces intervened and blamed the deaths on "pilgrims not following the rules."  But Mecca is by no means unfamiliar with disasters of this kind—in 1990, for example, nearly 1,500 people were trampled to death. The problem has become so severe that it has necessitated 300 video cameras and the creation of a command and control center to monitor the thousands of people streaming through.

This kind of experience has little resonance for modern Westerners, whose travels to the Holy Land today look more like recreational tours than death-defying treks. But the pilgrim impulse still animates many Jewish and Christian believers, as it does Muslims. While the Ministry of Information in Saudi Arabia reported last year that over 250,000 Muslim pilgrims had already completed their hajj to Mecca and Medina by early March, Pope John Paul II's visit to Israel in 2000 generated so much interest that US Catholic bishops drafted guidelines for pilgrims traveling to the Jubilee celebrations, and one online directory touts 14 travel agencies (serving both Catholic and Protestant clientele) devoted solely to religious pilgrimages.

So what is it that draws believers from each of these world religions to holy sites?

To start with, Islamic law requires Muslims to go on hajj—or pilgrimage to Mecca—once in their lifetime. Yet the journey has its own magnetism for the Islamic faithful. Muslims claim the vicinity of Mecca as the site of Hagar's wandering in the desert after Abraham and Sarah expelled her in Genesis 21. The story goes that Abraham visited Hagar there and, with Ishmael's assistance, built the first mosque ...