The Grotto of the Redemption is a religious monument which consists of nine grottos depicting scenes in life of Jesus. The Grotto contains a large collection of minerals and petrifications and is believed to be the largest grotto in the world. It is also "considered to be the world's most complete man-made collection of minerals, fossils, shells, and petrifications in one place." The total value of all the rocks and minerals which make up the Grotto is over $4,308,000.
From the book "Fantasy Worlds"