Exploring Underwater Ruins, Part II: “The Caissons” in Lake Michigan

While this site may not have the same caliber of mystery and age that the Yonaguni Monument possesses, it still represents an important piece of Chicago history.

After the Great Chicago Fire in 1871, Chicago was faced with an opportunity and a challenge. Chicagoans had the chance to change the face of their city, but even as they realized this they were left with a problem: what were they going to do with all the debris? The fire had consumed much of the primarily wooden city; there was wreckage everywhere.

Some of it was shoveled to the edge of the lake to serve as landfill as part of a project to extend the shoreline and create Grant Park and other public lake front spaces, but not all of it. They actually loaded much of the debris onto enormous barges, sailed due east of the Chicago River, and dumped it between 6 and 10 miles out into Lake Michigan.

How do I know this? Because now, it’s a dive site.

Though much of the debris is now buried, the site is diveable, marked by two caissons that were dumped as well as some ships and barges that were sunk loaded with garbage (including one that was burned to the waterline, then sunk). If you dive this site intending to do some treasure hunting, bring a hand trowel and be ready to get dirty; you can take whatever you find (since it’s considered garbage, it is not a protected area). There have been many objects pulled up over the years: bricks, china, weapons (including, if the rumors are true, Civil War-era daggers and swords), glass bottles, silverware, more bricks, gas streetlamps, porcelain, and bricks, to name a few (there are lots of bricks).

The bad news? The site stretches across four miles of lake; you could find something amazing, or you could find nothing, and you always have to dig in low visibility to find it. The odds may not be in your favor, but the history that Lake Michigan can yield should be enough to intrigue any adventurous spirit.

Special thanks to Captain Jim Gentile, owner of Windy City Diving, who answered my questions and passed along a couple of anecdotes. Check out his dive charters on Lake Michigan at his website: windycitydiving.net.

Exploring Underwater Ruins, Part 1: The Yonaguni Monument

If exploration is in your blood, there are some truly unique diving experiences to be had in the vast expanse of our oceans and waterways, not just on coral reefs or shipwrecks, but on the streets of submerged cities and ruins whose construction and destruction is often a mystery. They can be found around the globe or in our own backyard, and they are all worth exploring... If you can track them down. We'll start with one of the greatest mysteries of underwater archaeology...

Yonaguni Monument, Japan


These structures have puzzled scholars and scientists alike for decades. Discovered off the coast of Japan's Yonaguni Island in 1986, they appear to be large, complex pyramidal structures that have been chiseled out of the existing rockface, not placed there or constructed from free-standing rocks. The question is, chiseled by what?

There are two theories: that the monument is artificial, the remains of a forgotten (but very powerful) civilization, or that the monument is a naturally-occurring effect of erosion by strong current and rock movement along the sea floor. For a natural formation, there is a huge concentration of clean lines and angles.


Check it out with...
The man who discovered it, of course! http://www.yonaguni.jp/en/