Only once have I strolled around Point State Park in downtown Pittsburgh; that was about 10 years ago when the American Folklore Society held its annual meeting in a nearby hotel. Little did I realize that I was walking above the subject of a unique urban legend.

Of course I admired the impressive sight there of two great rivers flowing together to form a third, in the shadow of Three Rivers Stadium, where the Pirates and the Steelers play their home games.But a legend? I never heard of it until Terry J. Wood of the University of Pittsburgh sent me a copy of his favorite city view.

It arrived in a padded 8-by-10 envelope marked "Do Not Bend! ULs of Ohio River Valley." Inside was an oversize postcard containing a color photograph of the park taken from a bluff overlooking Pittsburgh's center.

A caption on the back of the card summarized the legend:

"The Great Fountain of Point State park has become a focal point and landmark of Pittsburgh's Golden Triangle. Largest in the U.S., this dramatic tower of water soars 200 feet at the confluence of the Monongahela and the Allegheny Rivers forming the Ohio. The Fountain's origin lies not in these three rivers but in a little-known fourth river underground."

"Little known," indeed! It seems like everyone who's visited or lived in Pittsburgh has heard this story, except me.

Not only do they know about the fourth underground river, but several present or former residents of Pittsburgh also repeated rumors about an airplane that years ago crashed into one of the two rivers feeding into the Ohio. Its wreckage was never found.

According to this story, the plane and its contents were swallowed up by the unnamed fourth river.

Another solid citizen of the Steel City told me about the terrible scare a scuba diver had when he ventured into the fourth river while working on the foundation for the U.S. Steel Building. Supposedly, he encountered albino catfish as big as calves living down there.

Actually, I've heard giant catfish legends told about many different bodies of water, but never about an underground river.

Does it exist, this "little-known fourth river"? Well, I said it was a legend, didn't I?

Helpfully, a few days later Wood sent me a copy of an article that debunked the story. Written by Kristen A. Velyvis, it appeared last August in the Pittsburgh Post-Gazette and began:

"Many people have sailed through life in Pittsburgh believing that a fourth river flowed under the city. Some imagined cavernous lakes and streams bubbling along under the surface.

"Well, it's not true.

"There is no fourth river under Pittsburgh. What you see is what you've got."

The article went on to explain that an aquifer (a porous and permeable sediment saturated with water) underlies Pittsburgh, but not a river. The water for the park's fountain is drawn from the aquifer, as is water for many downtown buildings, perhaps giving people the idea that an actual underground stream exists.

Velyvis gave a detailed geological explanation for the aquifer's formation, plus technical reasons why an underground river couldn't flow there.

It's probably a good thing, since if there was one, they'd have to rename the stadium Four Rivers Stadium, and that sounds funny.

I'm trying to collect urban legends from other major cities along the 981-mile length of the Ohio River, which runs all the way down to Cairo, Ill., where it flows into the Mississippi. For example, I'm told that in the 1950s some people in Evansville, Ind., thought that the Russians regarded their city as a prime nuclear target.

The idea was not that there were major military installations in the area, but that the huge bend in the river that occurs there offered an opportunity for mass disruption of commerce. As my informant put it:

"A good pop right on Fourth and Main would blow the Ohio out of its banks, sending it coursing off through Kentucky, and rendering it unnavigable for years, thus crippling all major cities upriver by eliminating at one stroke all the barge traffic."

Has anyone got any more ULs of the Ohio River Valley cities to send me?- "Curses! Broiled Again," Jan Harold Brunvand's fourth collection of urban legends, is now available in paperback from Norton. Send your questions and urban legends to him in care of the Deseret News.