Travel to a place held sacred, undertaken as a religious act. It appears in nearly every major tradition, it moves enormous numbers of people, and it has shaped trade routes, cities and the spread of ideas.

Pilgrimages differ greatly in destination and doctrine and share a recognisable shape.

There is separation from ordinary life, often marked by special dress, by abstaining from usual comforts, or by a formal act of departure.

There is the journey itself, frequently difficult by design. Effort and discomfort are treated as part of the act rather than obstacles to it, which is why walking routes persist where transport is available.

There is arrival at a place regarded as holy, usually associated with a founding event, a burial, an apparition or a relic.

There is return, with the pilgrim marked as having completed it, sometimes by a title, a token or a change in status at home.

Anthropologists have noted that pilgrimage tends to suspend ordinary social distinctions temporarily, producing a sense of equality among participants that does not persist afterwards, though the extent of this has been debated.

Members of a brotherhood of Jerusalem pilgrims, painted in the sixteenth century. Completing a pilgrimage conferred a recognised status that pilgrims recorded and displayed.
Members of a brotherhood of Jerusalem pilgrims, painted in the sixteenth century. Completing a pilgrimage conferred a recognised status that pilgrims recorded and displayed.Credit: Jan van Scorel (Public domain).

The Hajj to Mecca is required of Muslims who are physically and financially able, once in a lifetime. It occurs on fixed days in the Islamic calendar and gathers on the order of two million people, making it among the largest regular assemblies in the world. The logistics are correspondingly extreme, and management of crowd flow is a permanent engineering concern.

The Kumbh Mela, held in rotation at four locations in India, draws numbers estimated in the tens of millions over its duration, and is frequently described as the largest human gathering of any kind.

Christian pilgrimage centres on Jerusalem, Rome and Santiago de Compostela. The Camino de Santiago has revived substantially since the late twentieth century, with numbers rising from a few thousand annually to hundreds of thousands, many of whom describe their motivation as other than religious.

Buddhist pilgrimage focuses on sites associated with the Buddha's life, including Bodh Gaya, and on mountains and temple circuits across Asia. The eighty eight temple circuit of Shikoku in Japan is walked over several weeks.

A figure in pilgrim dress from the fifth century BCE. Travel to sanctuaries and oracles was an established practice in the ancient Mediterranean well before the traditions that dominate it now.
A figure in pilgrim dress from the fifth century BCE. Travel to sanctuaries and oracles was an established practice in the ancient Mediterranean well before the traditions that dominate it now.Credit: Zde (CC BY-SA 4.0).

Hindu pilgrimage includes the Char Dham circuit and journeys to the Ganges, particularly Varanasi. Sikh pilgrimage centres on the Harmandir Sahib in Amritsar. Jewish pilgrimage historically centred on the Temple in Jerusalem, and the Western Wall remains a focus.

Ancient Mediterranean practice included travel to oracles and sanctuaries, and pilgrimage to Ise in Japan predates Buddhist influence.

A pilgrim in the Himalayas. Routes established for religious travel have persistently doubled as routes for trade, information and the movement of ideas.
A pilgrim in the Himalayas. Routes established for religious travel have persistently doubled as routes for trade, information and the movement of ideas.Credit: John Hill (CC BY-SA 4.0).

Pilgrimage routes functioned as trade routes. Merchants travelled with pilgrims for safety and sold to them, and towns along major routes grew on the traffic.

They spread information and ideas. People from widely separated places met, and pilgrimage accounts are among the more useful surviving sources on medieval geography and travel conditions. Ibn Battuta's travels began as a pilgrimage.

They shaped architecture and urban form. Churches on pilgrimage routes were built with ambulatories allowing crowds to circulate past relics without disrupting services, and cities developed hospices, roads and bridges for pilgrims.

They transferred wealth. Offerings at major shrines were substantial, and competition for relics between institutions was commercially motivated as well as devotional.

Disease travelled the same routes, and mass gatherings have historically been associated with epidemic spread, which is why modern pilgrimages involve extensive public health measures including vaccination requirements.

Numbers are rising rather than falling, assisted by air travel and organised tours, which removes the difficulty that was historically part of the practice and has prompted debate within traditions about whether ease diminishes the act.

The boundary with tourism is not sharp. Many who walk major routes describe motivations that are cultural, athletic or personal rather than doctrinal, and sites depend economically on visitors of both kinds.

Management has become a serious technical field. Crowd dynamics at the largest gatherings involve genuine risk, and fatal crowd incidents have occurred at several, which has driven work on pedestrian flow that is applied well beyond religious contexts.

Pilgrimage is among the most durable of human practices, sustained across traditions that agree on almost nothing else, and it has moved people across long distances for religious reasons for at least three thousand years.

Its secondary effects are historically large: routes established for devotional travel carried goods, information, architecture and disease, and several of the world's enduring cities grew around the traffic.