OPPENHEIM, GERMANY–This jewel of a town, with its large cathedral, half-timbered buildings and narrow streets, share surprising geological connections with Vicksburg, Mississippi — a city visited by Wooster geologists earlier this summer. Both are river towns which profited in good times as trade centers, and both are underlain by Pleistocene loess sediments. Loess is wind-deposited silt and clay that can be easily excavated yet retain vertical walls because of the angular nature of its grains. Residents of both cities dug caverns into their loess deposits to store goods and to escape the dogs of war above them.
Model of a family hiding in a loess cavern underneath Oppenheim, Germany.
Oppenheim is almost completely undermined by up to 200 km of connected tunnels and cellars known collectively as the Kellarlabyrinth. The digging began sometime in the Middle Ages as a way to safely store and transport goods between buildings in the prosperous town. When the religious wars of the 17th century began, Oppenheim was almost continually besieged and occupied by one side or the other. The labyrinth below became a good place to hide from marauding soldiers. The system continually grew as the Oppenheimers dug laterally through the thick bed of loess below their town. The tunnels are still in partial use today after renovation and structural enhancement. In 1945 the American Army successfully crossed the Rhine near Oppenheim. As one of General George Patton’s tanks moved through the streets of Oppenheim, it crashed through the street into a tunnel below. Heavy vehicles have been rerouted around Oppenheim ever since!
You can't have an extensive Medieval cavern system in Continental Europe without some part of it turned into an ossuary. There are the remains of at least 20,000 people in the Oppenheim bone caverns.
