There are many reasons for this recognition. Assisi, with its Basilica and the importance of the artists who worked on it, is a cultural and spiritual inspiration to the world: the spread of the artistic and spiritual message of the Franciscan Order have influenced the art of other towns and cities. Assisi represents a unique example of a "city-sanctuary" within its environmental setting, from its Umbro-Roman and medieval origins to the present day. The Basilica of San Francesco is also considered to be an exceptional example of an architectural ensemble which has significantly influenced the development of art and architecture. Lastly, according to UNESCO, Assisi, as birthplace of the Franciscan Order, "has from the Middle Ages been associated with the cult and diffusion of the Franciscan movement in the world, focusing on the universal message of peace and tolerance".

Assisi, the town of Saint Francis, stretches out along the slopes of Monte Subasio. The long roads which sit at a reasonably high-altitude, cross the town, open onto the large piazzas in front of the Cathedrals of San Rufino, Santa Chiara and the Comune (the Town hall). A visit to Assisi is clearly intertwined with its Franciscan heritage. The sacred nature of the place has influenced the planning and architecture of the town, where the celebration of Franciscan ideology has contributed to the creation of monuments that are of outstanding architectural and artistic interest. This is a characterising and unusual phenomenon which suggests a way to approach and better understand Assisi itself.

With its medieval art masterpieces like the Basilica of San Francesco and frescoes by Giotto, Cimabue, Simone Martini and Pietro Lorenzetti, Assisi has become a fundamental reference point for the development of Italian and European art and architecture.