There are numerous references, some fictional, some not, to an underground river flowing beneath downtown Birmingham. UAB geology instructor George Brockman attested to the presence of a below-ground stream downtown. The floor of Jones Valley, like much of the Birmingham District, consists primarily of limestone karsts. Limestone is a relatively soft sedimentary rock which is easily worn and shaped by eons of water flow. Slightly acidic runoff can accelerate the formation of caverns which become sinkholes when they collapse.
 Early reports
- Early settlers were supposedly informed by Native Americans that an underground stream ran the full length of the county. According to Leah Rawls Atkins' 1981 history, The Valley and the Hills, "Indian children, when they came into the white settlements to trade at the stores, would play with pioneer children and tell them stories of how they had come from a long canoe ride on this underground river."
- According to a 1954 account by his granddaughter, engineer William Barker, who laid out the city's lot lines for the Elyton Land Company, was convinced of the presence of an underground river.
- R. H. L. Wharton purchased the "water privilege" for the infant city in 1871 and dug wells on 2nd Avenue North at 20th (in front of the Webb Building) and between 20th and 21st Streets. The latter well was reported to have struck an underground stream and to be inexhaustible. Wharton's wells were closed after the establishment of the Birmingham Water Works in 1872. A spring was still reported to exist below the Dude Saloon in the Webb Building that "used to supply the neighborhood with water." A third well in the center of the intersection of 2nd Avenue and 21st Street was reported to have had the bottom drop out of it.
- Asked in the 1880s, older citizens said they knew of a "lime sink" near 5th Avenue and 20th Street where cold water could be drawn up in buckets from far below.
- In his report on the 1873 cholera epidemic, physician Mortimer Jordan, Jr described the geology and water resources of the infant city thus: "Birmingham is located in Jones Valley, near the center of Jefferson County, with the Red Mountains lying a short distance to the south and east, and what is known as Reservoir Ridge to the north and west. The stone near the surface is blue limestone covered with a stiff clay soil, such as is usually found in the hilly portions of Central Alabama. The bed of the valley is formed by the old Silurian limestone which doubtless was brought to the surface through the superincumbent strata and is found throughout the entire valley, almost on edge, dipping, as we recede from the valley, to the northeast and southwest. From this fact we are led to conclude that the only water that appears on the surface or is found in wells in this valley must be surface-water, for the strata of limestone are not water bearing and only afford such supply of water as may have filtered through the strata of earth overlying the edges of this formation during the winter or rainy months which finds a ready outlet in a southwest direction along the line of upheaval. This water finds numerous outlets at various points in the valley as is shown by the location of the springs, to be seen on the accompanying map, all of which, with others northeast and southwest of Birmingham, are situated on the line of upheaval."
- In 1881 the area of Southside near 18th Street and 5th Avenue South was attracting a "large number of new settlers around the big spring", attracted by the convenience of fresh water.
- In 1883 a well-drilling team struck a small flowing stream of water approximately 300 feet below the surface.
- Milner Spring was located at 21st Street and Avenue D (4th Avenue South).
- In August 1884 it was observed, during a hard rain, that water flowing along a large, open sewer on 5th Avenue North, disappeared into the ground at a certain point between 21st and 22nd Street. An investigation revealed a hole in the bottom of the sewer opening into a large cavern. Mayor A. O. Lane directed an exploration by "two strong men with ropes tied around their waists", elsewhere identified as "Mr. Lacy, boss of the street gang, and a Negro man". The two worked their way through the rock and reported that they heard rushing water below, but could not locate the bottom of the cavern, even with 9-foot poles they took with them. Complaining of headaches from "impure air" they returned to the surface.
- The Birmingham Iron-Age of August 21 of that year reported that crews were working to open inlets to the underground river at 5th Avenue between 22nd and 23rd Street North, and at East Park, near Central High School. Mayor Lane was interested in determining the value of such a stream either for water supply or drainage. Later reports indicated that it was expected to be used as a sewer.
- These developments inspired a notorious tale-teller named Joe Mulhatton. He produced a sensational report of a huge river flowing beneath the city and endangering the entire area. His fictional report first appeared in the Louisville Courier-Journal, but was picked up by other newspapers afterward. Among Mulhatton's claims were that the city rested on a "crust" of stone only a few feet thick which had been broken open during construction of a large building. He claimed that many buildings had collapsed and that City Hall had settled 4 feet on one corner into a widening fissure. The city was "flooded with telegrams" inquiring about the calamity over the following days.
- The Birmingham Iron-Age dubbed the reported stream the "Mystic River", for its hidden aspect and for the "poetical ring about it which will prove of much value to aspiring poets and poetesses to illustrate." They demonstrated one such attempt thus: "We'll idly float / in fairy boat / where moonbeams never quiver. / We'll pull an oar / to foreign shore / down on the Mystic River."
- Not done with the story, Mulhattan also fabricated a report sent to the Birmingham Iron-Age and published on August 28 with the headline "Underneath Us", claiming that a group of leading citizens (including Joseph Smith, W. S. Brown, William Hood, T. J. Brown, William Berney, George Kelley, J. B. Earle and others), had contacted "Prof. Joseph Mulhattan" of Kentucky to investigate the city's underground river. After negotiating the narrow entrance, he claimed to have spent an entire Saturday with a small company exploring the 300-foot wide by 150-foot high by 15-mile long tunnel on an improvised boat. He reported that the 45-to-70-foot-deep river was suitable for steamship travel and "connected with tide water", meaning that the District's mines and mills could enjoy a direct route to sea. He concluded that his was "undoubtedly the most remarkable discovery ever made on the American continent," that the river was "greater in volume than the mighty Mississippi," and that its presence surely indicated that "prehistoric people" operated furnaces in Birmingham from which they supplied metals to "various points of the world". This last finding was justified by the discovery of "numerous articles of bronze, also statuary, numerous Masonic emblems, and mummies with sandals on their feet -- all in a perfect state of preservation" along the banks of the river. He also reported finding the remains of an ichthyosaurus, an example of an "extinct sea monster" which was "undoubtedly used by these prehistoric races to drag their ships from what is now Birmingham to the Gulf of Mexico." He viewed the hulls of just such ships scattered along the route. He further reported "numerous eyeless fish and eyeless sea-monsters of the shark species; also eyeless amphibian animals of the alligator and reptile tribe".
- Inspired by these reports, a "shrewd Selma negro" advertised excursions by boat in Birmingham's underground river and filled train cars with curiosity seekers who never managed to locate his boat landing.
- An October 22, 1885 edition of the Weekly Iron Age found the persistence of belief in a large underground river amusing. George Stonestreet, a sewer contractor, reported having been asked where the "big stream" was while his crew was working below 1st Avenue. Stonestreet replied that he "had not discovered it myself yet." He further explained that the lowest section of the city was the "flats below the Coketon Depot, and the highest point was "near the exposition building on 20th Street."
- A March 25, 1886 report by W. C. Kerr, engaged in boring wells for the Birmingham Rolling Mill, indicated that water from an underground stream filled his 500-foot borings to within 12-feet of the surface. Those pressing their ears to the top of his holes could hear water rushing below.
- A fantastical report similar to Mulhattan's earlier efforts appeared in the May 29, 1886 edition of the Birmingham Age, under the cryptic byline "H". It tells the story of a covert voyage in a stolen boat under the city, the discovery of Steve Renfro's hidden counterfeiting operation, and of eventually surfacing into the Warrior River.
- An office in the vicinity of 5th Avenue North and 22nd Street advertised "Mystic Underground River" excursions during the 1880s and 1890s.
 Avondale Cave
Also in the mid-1880s, an opening into a cavern behind the spring at Avondale Park became accessible and tempted curiousity-seekers who reported finding arrowheads and carved-out niches as evidence of prehistoric human occupation. One entrepreneur secured permission from Peyton King to quarry brown marble from the cavern, with limited success. Others reported observing the 20-foot-deep crystal clear underground stream that fed the park's springs. At one point a load of dye was introduced to the underground stream and its stain became visible later in Valley Creek near Rickwood Field. Less reliable reports involved young explorers emerging from the cave after entering an iron-ore mine elsewhere, or entering the cave and emerging elsewhere in East Lake much later. One fantastic story, printed in the Birmingham Age-Herald in 1886, told of a pair of explorers pilfering a boat from the lagoon and working it into the cave entrance where they attempted to row upstream to find the source of the underground river. Failing to do so, they drifted back downstream, missing the cave entrance, and proceeding to drift under the city of Birmingham, listening to the roar of furnaces and the rumble of trains. After passing the city, they spied a light high up in the darkness and, investigating, discovered a boat tied up at a small landing, from which a rickety stair ascended to a doorway carved into the rock. Through the door they could see a room where a young woman snoozed on a couch, a man engraved a metal block with a stylus, another man, an African American, worked a press, and a third man, who was outlaw Steve Renfro, presided over the counterfeiting operation. Not wishing for trouble, the explorers tiptoed back to their boat and returned to the current. After a restless nap, they awoke still in the cavern, but soon located a pinprick of light which eventually grew into an opening through which they emerged into the Warrior River. They continued as far as Tuscaloosa where they spent the night before taking a train back to Birmingham.
The entrance was sealed in the 1930s, but re-discovered later. A group of trained spelunkers mapped as much of the flooded cavern as they could in 1983, finding most of the passages disappearing quickly into mud-filled crevices.
 Later reports
- Access to an underground stream near Highland Avenue and 12th Avenue South was sealed by the city in the early 1900s because it posed a danger to children.
- A spring surfaced at 5th Avenue South and 22nd Street and was utilized for drinking water, and later as the site of the Birmingham Ice & Cold Storage Co., which drew from the stream until it disappeared.
- Construction of the Tutwiler Hotel (1914) was delayed by the need to add steel beams to the foundation in order to span the river's cavern.
- The never-completed Roden Hotel, begun in 1913 at 5th Avenue North and 18th Street was limited to a single-story basement because of groundwater.
- T. A. Weller of the Birmingham Chamber of Commerce referenced artesian wells and the report of the "president of the pipe works" that an underground river 30 feet below the surface would provide an endless source of industrial water.
- The Liberty National Building (1925/1971) pumps groundwater from its sub-basements and formerly used it to irrigate planters along 3rd Avenue South.
- The Florentine Building (1927), which was planned as a 10-story building, only went to 2 stories, partly because of the expense of shoring the foundation.
- In a story about the demolition of the William Barker residence, Birmingham News reporter Lane Carter noted that an underground stream was present on Southside and had caused cave-ins.
- The Federal Reserve building's 1957 annex was beset by foundation flooding. The excavation filled with clear water and was pumped out continuously during construction.
- A January 15, 1961 Tuscaloosa News article describes a sinkhole appearing in Midfield that swallowed about 25 square feet and a pair of shrubs from David Holland's front yard. The hole opened to a river about 15 feet below ground level and another 70 feet deep.
- Construction of the Daniel Building (1967) was delayed as engineers searched for areas of solid bedrock between limestone cavities on which to erect its caissons.
- Numerous downtown structures are said to use underground water, reached by wells, as part of their cooling systems.
- Flooding in the basement of the Thomas Jefferson Hotel after it became vacant was blamed on an "underground stream".
- The Ideal Building is said to experience frequent basement flooding from subsurface water.
- After the John A. Hand Building was vacated in 1994, flooding in the basement occurred and was attributed to the underground river.
- A sinkhole, reportedly more than 100 feet deep, appeared near the intersection of 15th Street and 3rd Avenue South during construction of Regions Field.
- A proposal to construct a pedestrian tunnel under 10th Street South connecting the Alys Stephens Center to the Abroms-Engel Institute for the Visual Arts was abandoned because "a river bed flows under the street".
- "Birmingham's Wonder: The Curiosities of an Underground Stream -- How it Was Discovered" (August 17, 1884) Atlanta Constitution
- "Some Early History: Among Which Recollections is the Time the Bottom Dropped out of the Well" (April 1, 1886) The Weekly Iron Age - via Birmingham Public Library Digital Collections
- "He Wanted to Know Where the Subterranean Stream Is." Weekly Iron Age
- "The First White Family" (April 15, 1886) The Weekly Iron Age - via Birmingham Public Library Digital Collections
- Walsh, William S. (1892) Handy-Book of Literary Curiosities. Philadelphia, Pennsylvania: J. B. Lippincott Co., p. 473
- Bryant, Walter (November 27, 1975) "Underground river helped shape city." The Birmingham News
- Bryant, Joseph D. (January 31, 2013) "Birmingham baseball stadium sinkhole patched but problems, challenges could linger, say geologists." The Birmingham News
- Heggen, Richard J. (2013) Chapter 87 "To Lie Like a Mulhattan", in Underground Rivers. Unpublished draft at unm.edu/~rheggen/UndergroundRivers.html