Crystal Cave: Descend Into the World's Largest Natural Geode

Why It Stands Out

The discovery of this subterranean treasure was an accident of industry. In 1887, workers digging a well for winery owner Gustav Heineman struck something much harder than soil.

They had punctured the wall of what would eventually be recognized as the world’s largest known geode. The walls of this chamber are studded with Celestine crystals, some of which reach lengths of three feet.

These bluish-gray formations create a jagged, otherworldly landscape that once filled much more of the cavity. In a strange twist of history, the cave is actually larger today because of the fireworks industry.

During the early 20th century, many of the crystals were harvested to be processed into strontium nitrate, a chemical used to produce red flames in pyrotechnics. While this mining removed some of the original splendor, it created enough space for humans to comfortably walk through the geode.

Today, the cave remains a centerpiece of the Heineman Winery, and the most popular way to see it is as part of a combined tour that ends with a glass of local wine, allowing visitors to toast to the geological luck of the Heineman family.

Before You Go

The cave is located on Put-in-Bay and is accessible via the island's ferry services. Because the space is quite intimate, tours are brief, typically lasting around 15 minutes.

It is a seasonal attraction, operating from late spring through the end of September. Given its location at a working winery, it is an ideal stop for those looking to mix a bit of natural history with a tasting of Ohio-grown vintages.