On May 13, 1917, three shepherd children reported seeing a luminous figure above a holm oak in Cova da Iria, a limestone hollow 130 kilometres north of Lisbon. Within three decades, that hollow had become the Sanctuary of Fátima, drawing four million pilgrims annually to a basilica complex larger than St. Peter's Square. The site's transformation from pastureland to pilgrimage destination reflects Portugal's deeply woven Catholic identity, but also a precise architectural response to mass devotion: the esplanade measures twice the area of Rome's Vatican forecourt, designed to accommodate 300,000 people during papal visits. Today, Fátima functions as both a working pilgrimage site and a study in 20th-century sacred architecture. The original Basilica of Our Lady of the Rosary, completed in 1953, rises 65 metres in Portuguese neo-baroque style, its limestone facade flanked by colonnades that frame the Chapel of the Apparitions at the esplanade's eastern edge. That modest chapel, rebuilt four times since 1919, marks the exact location of the reported visions. In 2007, the Sanctuary added the Basilica of the Holy Trinity, a circular concrete structure seating 8,633 worshippers beneath a 21-metre oculus. Architect Alexandros Tombazis designed it without interior columns, allowing unobstructed sightlines across a space nearly as wide as a football pitch. A Lisbon to Fátima half day tour typically departs between 08:00 and 09:00, reaching the Sanctuary by mid-morning via the A1 motorway. Most guided excursions allocate two to three hours on-site, allowing visitors to walk the esplanade, enter both basilicas, and visit the Chapel of the Apparitions, where pilgrims leave thousands of handwritten petitions daily. Many itineraries extend to Aljustrel, the hamlet two kilometres south where shepherd children Lúcia dos Santos, Francisco, and Jacinta Marto lived in stone cottages that remain open to visitors. The houses, preserved with period furnishings and worn flagstone floors, offer a material counterpoint to the Sanctuary's monumental scale. Combination tours often link Fátima with Batalha, Nazaré, and Óbidos, forming a 220-kilometre circuit through central Portugal's religious and coastal landmarks. Batalha's Dominican monastery, a UNESCO site 18 kilometres from Fátima, was built to commemorate Portugal's 1385 victory at Aljubarrota. Small-group departures, capped at eight to fifteen passengers, allow stops at viewpoints above Nazaré's clifftop Sítio district and time inside Óbidos' 13th-century castle walls, returning to Lisbon by early evening.