Rome and Assisi add a scarf or light jacket for air-conditioned churches and a refillable bottle for the city's drinking fountains. St. Peter's has no luggage storage and asks visitors to avoid oversized bags, so a day bag that fits under a seat is the right size. Assisi's lanes are steep and often wet; shoes with grip matter more there than in Rome.
The Holy Land adds a hat and sun protection for Galilee, a modest outfit with long sleeves for the Western Wall and any mosque visit, a swimsuit for the Jordan River renewal of baptismal promises (a white garment is usually provided), and a copy of the travel advisory's guidance on alert apps. The State Department recommends enrolling in STEP before any trip.
Lourdes adds a swimsuit or shorts for the baths, where pilgrims are wrapped in a cloth, and a candle holder bought on site rather than carried. Medjugorje adds walking poles or a stick for Apparition Hill and Cross Mountain, which are rocky, and a flashlight for the hills early or late. Fátima adds knee pads for anyone planning to walk the penitential path on their knees, and a warm layer for the open esplanade at night.
The Camino is the exception: the pack is the pilgrimage, and the existing Camino pages cover it. Everywhere, carry prescriptions with the written prescription and check restrictions with the embassy of each country, as the State Department advises, since some common American medications are controlled abroad.