283. In the Constantinian era, following the rediscovery of the places associated with the Passion of Our Lord and the of the relics of the Passion, Christian pilgrimage made significant progress: pilgrimage to Palestine was especially important in this regard, since its holy places, starting with Jerusalem made it a “Holy Land” . Contemporary accounts make this clear, as can be seen in the fourth century Itenerarium Burdigalense and the Itenerarium Egeriae.
Christians emerged from houses and catacombs to worship at important locations:
Basilicas were built on the site of the “holy places”: the Anastasis on the Holy Sepulchre, the Martyrium on the Mount Calvary, and quickly became places of pilgrimage. The sites associated with the infancy and public life of Christ also became places of pilgrimage. Pilgrimages began to be made to some of the site associated with the Old Testament, such as Mount Sinai.
The Directory on Popular Piety and the Liturgy is online at the Vatican site.