The five-and-a-half miles of Indiana's Marengo Cave have some amazing natural formations underground.  But one of the most amazing features of the cave isn't natural at all. You'll find it by heading straight down - and making a left turn in Bernson's Corner.

Marengo Cave was first discovered back in the 1880s, and sometime after that, in one particular cave room, someone found that a coin tossed into the humid cave air would stick to the mud on the ceiling. 

Cave guide Larry Wyman says, "we've known back from the 30s and 40s people have been doing it -- but we're really not sure how far back it really actually started, no idea."

Every ten years or so, the cave staff has to climb ladders and harvest the money off the ceiling -- which is, as far as we know, the world's only upside-down wishing well.

Wyman explains, "well, there's mud up on the ceiling which is actually from the last glacier period - left behind, where water washed all the silts into the cave here."

Larry Wyman and Jeff Knieriem will spend several days, 20 feet above the cave floor, collecting mostly pennies that have oxidized to a green color.  The pennies haven't been cleared off since 1999.

Knieriem says, "some of 'em are really hard to see the dates on 'em, because they've oxidized so much that the date is unrecognizable. I think the last time we got like 500 pounds of coins." That added up to about three-thousand-800 dollars. 

The money collected this time will be donated to the Crawford County Library." 

The guys also find other things like photo-flash cubes, house keys, pens, pencils, a blue plastic comb, and a Chapstick.

The best story happened a few years ago when an engaged couple was touring the cave.

Knieriem explains, "they got mad at each other on the tour.  And she just decided that she didn't want to get married any more.  And so she tossed her engagement ring on the ceiling.  And then we had to come back down here and get it with a ladder, because she changed her mind."

There's been good news for the sputtering American economy lately: on the rise are the stock market, housing starts and employment.  And -- according to the ceiling of Marengo Cave -- cash is up too. 

From Crawford County Indiana -- Barry Bernson, Fox 41 News.