The crypt was formed by a nave and two side aisles with gothic vaulted ceilings. A notable feature being the 28 enormous pillars of grey marble which support the weight of the Upper Basilica constructed on top of it. The central altar was rebuilt in 1966. Above the altar there is a statue of the Madonna and Child which was sculpted in 1868 by Joseph-Hugues Fabisch. It is enclosed by four chapels dedicated to the Sacred Heart, Saint Peter, Saint Joseph, and Saint John the Evangelist. The shrine is in Saint Joseph's chapel and was built by goldsmiths from Lyon - Armand, Calliat, Catelant. Bernadette's fifth right rib, appropriated during the third exhumation in 1925, is house there.
Hewn out of the rock, the Crypt is surprisingly small, which helps to reinforce its stability. Until 1904 entry into the Crypt was through two underground passages. These were closed and reinforced in order to strengthen the foundation of the Upper Basilica built right above the Crypt. Nowadays, the Crypt is accessed by means of a central passage. To the right of the entrance is a large bronze statue of St. Peter holding the keys to the Kingdom of Heaven. Opposite stands a bronze statue of Pius X administering the Eucharist. Next to this is the statue of Bernadette depicted as the shepherdess of Bartres.
On the pediment above its entrance is a medallion of Pope Pius X, author of the decrees on frequent communion and the communion of children. In front of the Crypt is the church courtyard beneath which, at ground level , is the Rosary Basilica. From the square one can see the grotto of the apparitions, the Gave that flows right in front of it, the castle and most of the hotel area of Lourdes
In winter, the faithful come to the Crypt to adore the Blessed Sacrament. This is also possible all through the year at the Adoration Chapel next to Saint Bernadette's Church and in summer, at the Adoration Tent erected in the meadow during the day.