Lawton's 1929 Sewer department map illustrating the layout of Schiek's Cave.
The cave beneath downtown Minneapolis has received occasional publicity from the late 1920s into the present day, and was variously known as the Loop Cave, old Bank Cave, and the Farmer's and Mechanic's Bank Cave. As the F&M Bank is currently occupied by Schiek's Palace Royale nightclub, the cave is generally referred to as Schiek's cave in modern exploration accounts. For those without the power to close downtown streets in order to open a manhole, the only access has historically been via the deep sewer tunnel below Minneapolis, the raging river of sewage known as the NMT. Few large cities (St. Louis being a notable exception) can claim to have natural caverns beneath the heart of their downtown business districts, so the existence of such a cave beneath Minneapolis has sparked a great deal of interest among geologists, historians, cavers, and urban explorers. The difficulty of reaching this cave has added to the mystique, making it a semi-legendary destination which few have ever seen. Recently we discovered a new route into the cave, which while still difficult, avoids the health and safety danger of the sewers. The full details, while very interesting and historically significant, would unfortunately compromise the future use of this route, and as such have been removed from this version of the writeup. From the speed with which the cave manhole was welded after photos appeared on another site, it's well known that MSP Public Works keeps an eye on websites like this. Some history and a brief account of exploring the cave are given below, or you can skip straight to the photos. You can also read more about Minneapolis drains and sewers here.
Rediscovering Schiek's Cave
First, some history.
The history of Minneapolis's underground begins long before human settlement, with the formation of alternating sandstone and limestone layers close to the surface of the Minnesota prairies. The existence of a relatively thick but loose sandstone layer topped by a thin, hard limestone cap created the potential for large, stable, and rapidly-formed cavities just below the surface. The indigenous inhabitants found many natural caves along the banks of the Mississippi, some formed by floods carving out sandstone banks, and some formed by springs leaching down through the sandstone and washing away the soft material. White settlers found this geology particularly useful for digging water raceways, sewer tunnels, and storage caves, which soon honeycombed the more developed sections of riverbank as the Twin Cities developed.
Until the turn of the century, the city of Minneapolis relied on a number of private septic pits and a few short riverfront pipes for its sewage needs. Mill tailraces often served dual use as sewage and hydropower outfalls, but reached only limited areas. Nearby St. Paul began carving an intricate labyrinth of sewer tunnels beneath its streets in the late 1800s, but Minneapolis was burdened with a much thicker limestone layer which made access to the deep sandstone more difficult. The solution, designed by city engineer Andrew Rinker, was to construct a very large, high-volume sewer interceptor tunnel beneath the heart of downtown, and connect homes and businesses thorough a network of deep side tunnels and shallow feeder pipes. While nowhere as extensive as St. Paul's 6'x3' sandstone and brick network, the North Minneapolis Tunnel, or NMT, was a much larger and deeper tunnel, with an inside diameter of 9.5ft, a vaulted brick and stone ceiling, and a flattened invert (floor). Feeder tunnels stretched down several major downtown streets in a tree branch pattern, with dropshafts from shallow pipes penetrating the limestone cap to connect to the deep system. Excavation was done both by hand tools and by hydraulic pressure, the sandstone could be carved out simply by blasting it with water jets and allowing the sludge to ooze out into the Mississippi.
While constructing the NMT around 1900, work crews broke through into several natural cavities beneath downtown and elsewhere. While most were relatively small voids, the one beneath the then Farmer's and Mechanic's Bank was quite large, spanning half a block, and reportedly contained many flowing streams, pools, and a waterfall dubbed “Little Minehaha Falls” pouring from a ceiling fissure. The NMT was continued through and just below the cave, with an access shaft and door added. Reports from the period are quite sensationalist while being vague on actual details, so the original condition and early history of the cave are difficult to determine. At some point prior to discovery, an artesian well pipe had been driven through the cave, and leaks from this well were considered a possible explanation for the cave's formation. Sometime before 1904, a shaft was bored to the surface with a ladder and hexagonal sewer lid installed, and a sewer connection from the F&M bank was passed through the cave and into a tunnel leading to the NMT. In the mid 1920s, the city of Minneapolis quietly commissioned work to shore up the cave's limestone ceiling and divert the natural water flows. Two maps were produced by the sewer department, in 1904 and 1929, showing a great deal of change in the cave's condition during that time.
The original NMT was designed to funnel all of Minneapolis' waste directly into the Mississippi just below the West Side milling district. In the 1930s there began to be greater concern for public health and pollution, and the tunnel was extended south and combined with other existing interceptors to form a tunnel leading all the way to St. Paul. Pipes siphoned the flow beneath the river, and the result of two cities' and numerous suburbs flushes eventually ended up at the Pig's Eye treatment plant, still in use today. Under Minneapolis, the NMT was diverted south at the intersection of 6th and Washington, and a new tunnel was dug northwest up Washington Avenue from this point to Hennepin avenue. This new tunnel served as a storm drain, carrying only rainwater and occasional sewer overflows, and outfalling into the former NMT discharge tunnel below the milling district. Branches reached up several major streets downtown, sometimes following the sewer tunnels at a slightly higher level, but only connected to the sewers at a few points.
Drain construction reportedly revealed several other natural caves beneath downtown, but the location and size of these cavities is quite vague, and any formal studies or exploration remain lost in sewer department files. Various secondhand reports place the next largest cavity somewhere to the southwest of Schiek's, and describe it as being a 65ft by 22ft triangle. Evidence of cavities in the area can be seen in one large and amorphously shaped drain chamber near this location, which appears to be a natural void lined with spraycrete and incorporated into the tunnel.
Exploring the systems.
The geological and cave resources of the Twin Cities have been of interest to various groups off and on through recent history. In the 1940s and 50s, a number of studies considered turning Schiek's and other caves into bomb shelters, but concluded that artificial brewery and mushroom caves were more suitable. Plans for a subway system in the 1980s produced a number of expertly researched but poorly depicted maps of all known caves and tunnels beneath the cities. Developers have proposed extending retail and commercial space downwards to maximize property use, creating mined-space structures similar to Kansas City's limestone quarry warehouses. So far the only practical application of these projects are a few underground buildings on the University of Minnesota's campus. After the brief 1970s oil crisis was over, energy-efficiency ceased being important to city officials.
People have been illicitly exploring the tunnels of major cities for as long as such tunnels existed, and Minneapolis is probably no exception. Reports of unofficial visitors to the loop cave date back to the 50s and 60s, and in the late 1970s a group of guerrilla cavers made a late-night run to pop the hex lid and lower themselves into the cave on a truck winch. In the late 90's, a website known as the Minneapolis Drain Archive chronicled the adventures of a group dedicated to finding their way into Schiek's cave from below. These explorers, led by Peter Sand, discovered a number of interesting tunnels and features below Minneapolis. They sailed up drains in canoes, swam into flooded tunnels, mapped out the networks of tailraces and forgotten mill tunnels below the city, and occasionally faced death or serious injury by drowning or high-velocity liquid. Eventually they determined a route to Schiek's cave via the NMT with the help of local caver Greg Brick. Entering the interceptor sewer far upstream, Sand's group traveled down to the cave access shaft and later emerged via the regulator at 6th and Washington. This structure was referred to as the “Death Holes”due to the frightening small apertures the sewage travels through before turning south at the junction with the drains. Soon afterwards, Brick visited Schiek's several times via breaks in the concrete tunnels, which offered a shorter and less dangerous route until discovered and sealed by the city sewer department. After the repairs were completed, it seemed that Schiek's cave was again unaccessible to anyone unwilling to brave the full length of the NMT or to face the wrath of police waiting at the top of a rope.
One day I found myself and a few other people mysteriously transported by magical fairies to the heart of Schiek's Cave. Well, the actual explanation is much more interesting than that, and in fact much more interesting than the cave itself, but requires some secrecy. Skipping directly to the cave found us in a series of low rooms and chambers. We checked out a few famous sights like the NMT connection, Little Minehaha Falls, the sewer to Schiek's nightclub (not human sized), and the shaft to a hex lid set in the street 75 feet above us. We contemplated exiting this way, but could see cars running over the lid occasionally.
The general appearance of Schiek's is a low (generally 5ft) wide space with muddy brown walls and floor, and a yellowish-brown limestone ceiling. There are few if any natural features like stalactites or soda straws, although the area around Little Minehaha Falls has some interesting calcium deposits on the walls and floor. Plastic straws, tampons, and other sewage-related artifacts cover the floor near the strip club sewer connection. Cement pillars appear frequently, installed to support the roof in case of collapse. Iron brackets from previous surveys protrude from the ceiling in an effort to bash the heads of explorers, and many other signs of human modification are everywhere. The main passages form a series of loops, which have apparently been dug out to enlarge the walking space, with some rubble dumped in other parts of the cave making the ceiling clearance very low. Earlier reports described the ceiling as being 8 or 10 feet high, so either these were exaggerated or sediment and rubble from sewer floods has been slowly filling the cave. Very low crawlways led off in several directionsbut are mostly dead ends.
Seeing the way local city workers have pointlessly destroyed other fine natural caves (such as Fountain's), I have little faith in the future of Schieks. One of these days it will probably be pumped full of concrete to balance a car park or use some surplus city budget. When that day comes, or when circumstances change recarding the secretive magical fairies, I'll post the full story and the rest of the photos here.
While much of the cave appears the same, there are a few notable landmarks. The shaft to the surface features broken hex lids dropped by careless workers (hex lids are a remarkably poor design, an akward size and weight combined with a shape that is hard to seat properly in the collar, but easy to drop down the shaft). Also prominent is the doorway into the NMT connection. The center photo shows the sewer tunnel connecting two sections of cave, and displaying overflows from the nightclub's sanitary connection. The last two show the room containing "Little Minehaha Falls", and some of the mineral formations along the limestone fissure from which the falls emerge.
One of the older brick pillars in the main section, and the sewer connection to Schiek's nightclub.
Most of the cave is low-ceilinged and "muddy", although the mud is probably sewer sediment.
Elsewhere in the voidspace, strange mucus bubbles form in the remains of past floods.