This is the Loretto Staircase. It was built in 1879 by a mysterious man who showed up after some nuns made a novena to St. Joseph, the patron saint of carpenters. They needed a stair to the second floor of the church and no locals could build it. So this guy shows up with just a hammer, a saw and a T square. He never said his name and left without getting paid. The stair has no visible means of support in the center. He used no nails. The species of wood he used does not exist. As recent as 1997, a wood scientist could not identify the the species, so he made up a new name just for this wood. Modern day engineers cannot figure out how this thing hasn't collapsed or how it is supported. The PBS show 'Unsolved Mysteries' did a documentary on this work of art. Very interesting!