Grotto of the Redemption 
West Bend, Iowa
Construction begun 1912
Father Paul Dobberstein labored from 1912 to his death in 1954 on this spectacular shrine, which remains unfinished. Claiming to be the largest grotto in the world, the property contains an enormous collection of minerals and gems and hosts more than 100,000 visitors annually.
Photo courtesy of Mary Schmiesing, © 2006 CatholicHistory.net
Link