People from everywhere come to St. Mary's Grotto to meditate and pray in its dimly lighted, cool, rock-like setting. The Grotto is modeled after the Shrine in Lourdes, France where the Virgin Mary appeared to Bernadette Soubirous in 1858. The production of the cave-like interior of the Grotto was fashioned in the studios of the Daprate Company of Chicago; Mr. Bell of the Carian Company reconstructed the Grotto in Rockford. He was well known for his plasterwork from other public buildings in Rockford.
The windows of ruby and dark blue glass were made in the studios of the Flanigan Biedenweg Company of Chicago from fragments of glass, which Mr. Flanigan had collected in Europe from church windows destroyed during World War I.
Below the Shrine to Our Lady of Lourdes with St. Bernadette in adoration, there is a flowing stream that is reminiscent of the miraculous stream in Lourdes. There are also shrines to St. Theresa and St. Anthony in the Grotto.