The Gave de Pau river runs through the heart of Lourdes, separating the sanctuary domain from the commercial town. It was at the bank of this river, beside the Grotte de Massabielle, that Bernadette Soubirous had her first apparition. The grotto itself is set into the cliff at the river's edge, and walking the path along the Gave is the way to understand the geography of the pilgrimage site — the river, the rock, the natural cave, the meadow where Bernadette was collecting wood.
The riverside walks on both banks of the Gave are pleasant and accessible, with bridges connecting the two sides throughout the sanctuary complex. The river runs fast and clear, fed by snowmelt from the Pyrenees. In the evening, when the candlelight procession fills the Esplanade and the sound carries across the water, the combination of the mountain river, the illuminated basilicas above, and the singing is one of the more unexpectedly affecting scenes in France.