The evaluation of touristic trips that people make in order to realize their religious beliefs, outside the places where they constantly reside, work and meet their usual needs, within the scope of tourism is defined as Faith Tourism. Religious tourism refers to all travel outside the usual environment for religious purposes, excluding travel for professional purposes (e.g. priests travelling for work).(UNWTO, 1995).

Faith tourism contributes to the development of world tourism, the spread of universal peace and understanding, economic recovery, socialization and the development of centers of faith. In this context, İstanbul , which contains the sacred places of worship of the heavenly religions, is an important faith tourism center with historical mosques like Hagia Sophia Grand Mosque, churches like Iron Church, St. Antuan Church, synagogues like Neve Shalom. 

United Nations World Tourism Organization (UNWTO)
https://www.e-unwto.org/doi/epdf/10.18111/9789284420858