Lourdes is a small town in southwestern France, located at the base of the Pyrenees Mountains. In medieval times, it was an important fortress town, but now it is chiefly a pilgrimage center. In 1858 the Blessed Mother appeared to a 14-year old girl named Bernadette Soubirous in a grotto above an underground spring that flows into the adjacent Gave River. Between February 11th and March 25th, there were 18 apparitions. In the last apparition, Mary said "I am the Immaculate Conception" in response to a plea from Bernadette to tell her who she (Mary) was. Bernadette later joined the Sisters of Nevers and was a member of that order until her death from tuberculosis in 1879. Her incorrupt body lies in a coffin of gold and glass at the Chapel of Saint Bernadette at the mother house of the order in Nevers, France. The basilica of Lourdes was completed in 1876 and is built above a large underground church. The underground church, the Basilica of St. Pius X, was built in 1958 and is the world's largest underground church. It can accomodate 20,000 people. The water from the spring in the grotto is believed to have special healing powers and has been the site of many miraculous physical cures -- crutches from hundered of cured paralytics are displayed on the walls of the grotto.