The Sanctuary of the Madonna di San Luca sits 300 metres above Bologna's terracotta rooftops, reached by the world's longest porticoed walkway — 3,796 metres of continuous arcade sheltering 666 arches that climb Colle della Guardia in fifteen chapels. Construction began in 1674 to protect pilgrims from sun and rain, funded by civic donations and completed over a century of incremental labour. The red tourist train now traces Via Saragozza's slope, departing from Piazza Maggiore and threading the portico's shadow to deliver visitors to the baroque basilica without the two-hour ascent on foot. The sanctuary has anchored Bologna's spiritual geography since 1194, when a Greek pilgrim carried a Byzantine icon of the Virgin and Child from Constantinople. That portrait, believed painted by Saint Luke himself, drew medieval worshippers up the hillside long before the portico existed. During plague outbreaks and sieges the icon was carried down to the city centre, a ritual that persists each May during the Feast of the Ascension when tens of thousands follow the procession route. The basilica's elliptical nave, completed in 1723 by Carlo Francesco Dotti, frames the icon behind an ornate silver altar. Today the San Luca Express Bologna tickets tour operates daily from mid-morning to early evening, its open-sided carriages allowing unobstructed views of the portico's rhythm and the Emilian plains spreading north toward the Po River. The onboard audio guide synchronises commentary with each chapel and curve, noting architectural details invisible to pedestrians: the varying vault heights, the Renaissance frescoes in the Arco del Meloncello gate, the shift from urban stone to rural brick as the arcade ascends. At the summit, visitors disembark into the sanctuary's colonnaded forecourt, where the panorama encompasses the Apennine foothills and Bologna's twin medieval towers piercing the haze. The railway's convenience has made the sanctuary accessible beyond pilgrimage season. The round trip includes time to explore the basilica's interior, examine the ex-voto offerings lining the walls, and photograph the city from the terrace before the return descent. Winter fog often erases the valley, leaving only portico and sky. Summer evenings stretch golden light across the arches as the train winds back toward Piazza Maggiore, the basilica's dome receding above the unbroken arcade that defines Bologna's silhouette as firmly as any tower.