Muslims participate in many types of travel that combine spiritual and mundane goals. For pious Muslims, nearly every journey has a religious dimension. Historically and currently, the most popular forms of religiously inspired travel include the pilgrimage to Mecca (ḥajj), the off-season, lesser pilgrimage to Mecca (ʿumrah), visits to hundreds of holy places throughout Asia and Africa (ziyārahs), study at Islamic schools and universities (madrasahs), reunions of transnational mystical orders (ṭarīqahs), missionary activity among both Muslims and non-Muslims (daʿwah), private business transactions guided by sharīʿah principles, diplomacy representing Muslim governments and international organizations, and journeys of exploration surveying the global Islamic community (ummah) and assessing its role in world affairs.

A typical traveler often combines several of these activities in a multipurpose journey, especially when visiting several destinations over an extended period of time. For example, most pilgrims to Mecca (ḥajjis) also visit Medina to pray at the Prophet's mosque and to see his tomb. Many people combine a ḥajj with stopovers at other holy places along the way. Asian ḥajjis frequently adjust their itineraries to include popular sites in Konya, Damascus, Jerusalem, Baghdad, Karbala, Shīrāz, Mashhad, Multan, Ajmer, Mazār-i Sharīf, Samarkand, Quanzhou, Demak, and Yogyakarta. For African pilgrims, the routes to and from Saudi Arabia often pass through Fez, Cairo, Kano, Touba, Capetown, Khartoum, and Harar. In all of these places, pilgrims are not merely worshipers but also traders, students, preachers, emissaries, demonstrators, explorers, and itinerant workers. Many also become fugitives, illegal immigrants, or smugglers.

Religious travel in Islam reflects an extraordinary degree of intercontinental cooperation among constantly intersecting groups that perform overlapping functions. The general pattern resembles a web of interlacing and autonomous networks instead of a rigid hierarchy, spontaneous collaboration rather than central direction, and fluid process over fixed structure. This vast web encompasses Muslims in every part of the world, helping to create a universal Islamic identity that transcends nationality, race, gender, and class. The ḥajj has always been the most powerful expression of Islamic unity and egalitarianism, and today its unprecedented size and diversity make it more important than ever.

Religious travel helps to sustain multitiered loyalties among Muslims, allowing them to identify with universal, regional, and even parochial communities at the same time. By guaranteeing the continuous interplay of unity and diversity, the web of religious travel fosters simultaneous pride in a single worldwide faith, in multiple cosmopolitan cultures, and in dozens of ancient ethnicities. Students of Islamic civilization have long appreciated the inherent tensions between these identities and the need for every Muslim society to renegotiate them periodically. However, they have not always understood how religious travel helps to make this coexistence and accommodation possible.

Most religious travel, including the ḥajj, is organized around linguistic and ethnic communities that participate in the global ummah while preserving a distinctive personality for diverse transnational cultures. The core groups define themselves in terms of common or closely related languages, particularly Arabic, Malay-Indonesian, Persian, Urdu, Turkish-Turkic, Hausa, Swahili, English, and French. Each of the major languages of the Islamic world evolved as a lingua franca facilitating the integration of multiethnic empires, intercontinental markets, and Diaspora communities. Many are hybrid languages and even when their structures differ widely they still share a vast vocabulary, particularly in religion, politics, and philosophy, that reflects common ideals and experiences.

All of these communities have an intercontinental reach and most also predate the rise of Islam. They are smaller than the ummah but much larger than states and nationalities, and they have developed different relationships with non-Muslim neighbors and Western colonialists. Each core community has made a special contribution to the evolution of Islamic civilization, the rise of modern nationalisms, and widespread intercultural borrowing between Muslims and non-Muslims. Thus, Islamic civilization is an amalgam of amalgams—a pluralistic family of overlapping transcontinental communities in which a handful of dominant languages help to forge common identities among disparate ethnicities and subcultures. Religious travel is one of the linchpins that unites and rejuvenates Islam globally and regionally. The constant intersection of multiple networks of religious travel is the lifeblood of the universal ummah as well as the transcultural linguistic communities that comprise it.

Every region of the Islamic world has a handful of cities that are particularly important crossroads because they blend a host of religious activities and radiate multiple layers of symbolic meaning. Some of the most notable examples are Konya in central Turkey, Yogyakarta in south-central Java, Kano in northern Nigeria, and Kashgar in far western China. These regional hubs attract an enormous flow of travelers and ideas moving back and forth between their neighboring hinterlands and Mecca. They are critical meeting points where the primordial and the cosmopolitan collide and transform one another in countless ways every day.

Konya's soul lies in the emerald-domed mosque and mausoleum of Jalāl al-Dīn Rūmī, patriarch of the Mevlevî mystical order known throughout the world as the “whirling dervishes.” The tomb of Mevlâna (“our guide” or “our teacher”) is the preeminent pilgrimage site in the Turkish-speaking world, but it also attracts non-Turkish Muslims who know Rūmī's Ṣūfī poetry in Persian, as well as followers of many other religions who admire his ecumenical and humanistic spirit. Konya is an important educational center for both mainstream and mystical Islam and it hosts a thriving religious publishing industry. The confluence of rich agriculture and private industry has made it one of the leading “Anatolian tiger” economies, and all of the conservative political parties that have ruled Turkey in recent decades enjoy wide support there. Beyond its spiritual, economic, and political importance, Konya is a powerful force in reviving traditional Turkish culture, including handicrafts, folklore, music, and archeology. Konya's genius is its ability to display its religious vitality through multiple personalities—Anatolian and Turkish, pan-Islamic and trans-sectarian, pre-Ottoman and post-modern—managing their inherent contradictions while profiting from the global reach of their combined appeal.

Yogyakarta plays a similar role in linking rival Indonesian expressions of Islam with the international mainstream as well as with indigenous Javanese culture. The Sulṭān's palace is a traditional center of Ṣūfī learning and a generous patron of local arts. The palace's ties with the rural population contrast with the urban middle-class following of the Muhammadiyah, the modernist mass movement whose founders were inspired by Egyptian and Arabian reformers and whose branches extend to trading communities throughout Indonesia, including remote parts of the outer islands of Sumatra, Sulawesi, and Nusa Tenggara. Despite its relative poverty, Yogyakarta continues to compete with Jakarta both culturally and politically. Its publishing houses and bookshops offer the richest variety of religious and secular titles in the country. Together, the mysticism of the palace and the modernism of the Muhammadiyah have encouraged record-breaking levels of pilgrimage in many forms—to local shrines in Yogyakarta, to the northern coastal cities that are resting places of the Wali Sanga (the “Nine Saints” who pioneered Islam in Java), and especially to Mecca for the ḥajj and ʿumrah. Each year Indonesia sends the world's largest delegation of ḥajjis to Mecca—about 200,000 annually—and many more make the ʿumrah. During the last forty years, Yogyakarta has been a driving force behind the rapid spread of Islam in Java and the rest of Indonesia. Its religious, intellectual, and political leaders have contributed greatly to Indonesia's growing influence in international diplomacy in the Islamic world and beyond.

Kano sits astride a wide belt of Hausa settlement and trade stretching across the African savanna from the Atlantic Ocean to the Red Sea. Pilgrims of the Tijānī and Qādirī mystical orders come to Kano from many countries, sometimes taking a long circular route via Egypt, Morocco, and Senegal before proceeding to Mecca and Medina. Kano enjoys a brisk traffic of illegal ḥajjis from neighboring countries such as Niger and Burkina Faso who use Kano as their gateway because they can buy foreign exchange and import contraband more easily in Nigeria than in their homelands. Kano boasts the most pluralistic collection of Islamic organizations, business interests, and political parties in northern Nigeria. The combination of sectarian, economic, and ideological rivalry generates constant turmoil and creativity throughout Nigeria and sub-Saharan Africa. Saudi Arabian officials are more worried about trouble-making pilgrims from Nigeria than from any other country. The Saudi government regularly accuses Nigerian ḥajjis of carrying infectious diseases, overstaying their visas, and belonging to international criminal gangs. In contrast to Indonesia where the pilgrimage boom has helped to increase diplomatic clout, Nigeria's rocky relations with Saudi Arabian ḥajj authorities have undermined Abuja's efforts to play a stronger pan-African and pan-Islamic role.

Kashgar is an historic Silk Road entrepôt linking China and Central Asia to the Middle East that has benefited greatly from post-Mao China's increasing links to the Islamic world. Kashgar retains a majority Muslim population of Uighurs, Kyrgyz, Kazakhs, Tajiks, and Türkmens. Unlike ürümqi, the richer capital of Xinjiang province, which is sharply polarized between dominant Han Chinese immigrants and a marginalized indigenous community that is mostly Uighur, Kashgar's multiethnic environment promotes a religious and cultural openness that is a striking contrast to ürümqi's communal tensions. New investment from the Middle East as well as Beijing has rebuilt the central business district around the majestic Id Gah Mosque. The media and schools are trying to promote a polyglot population and bookshops are teeming with bilingual and trilingual materials for all ages in Uighur, Chinese, and English. As Beijing encourages Islam domestically in order to strengthen its diplomatic and commercial ties with the Islamic world, Kashgar is poised to reemerge as a pan-Asian hub for religious and commercial travelers.

Each of these cities—and dozens more in the Arab world, Iran, and South Asia—exposes Muslims from all classes and cultures to multiple expressions of a common faith. Their constant interaction has helped to sustain a worldwide civilization for more than a millennium. Long before Western scholars discovered the importance of globalization and transnational networks, Muslims were experiencing them as concrete realities every time they left their homelands to worship and to explore a world that they have always viewed not as a shifting jumble of man-made nations, but as a seamless creation of God.