Two new "lakes" were discovered deep within Jewel Cave during a recent caving expedition. This one was named New Year's Lake/NPS, Dan Austin

Every now and then, Jewel Cave reveals a secret.

That was the case during the year-end holidays, when a group of spelunkers headed into the national monument in western South Dakota for four days and came back with photos of two "lakes" deep within the cave.

In what has become an annual tradition, explorers entered the cave on Friday, December 30, for a four-day trip. They traveled to the recently established Deep Camp on the southwest edge of the known cave. While there, they mapped and surveyed an additional 9,777 feet of new passages. This extended the length of Jewel Cave beyond 185 miles. 

When the team celebrated New Year’s Eve at base camp, no one could have been prepared for finding two new lakes on January 1. With water being rare and only found in less than 1 percent of the known cave, the discovery of additional lakes is exciting for the monument’s future. Cavers found a 70-foot long, 15-foot wide lake - aptly naming it New Year's Lake. Shortly after, they found a smaller, 15-foot diameter lake, calling it Bonus Lake.

“With the establishment of a third base camp in Jewel Cave, opportunities for discovery are quite literally waiting in the shadows of unexplored leads. With the dedication of specially trained volunteer cavers, more secrets of Jewel Cave will be revealed," said Superintendent Bonnie Schwartz.

“Based on the geology and hydrology of the area, I predict that we’ll be seeing many more lakes to come. No one knows for sure what the new discoveries will reveal, but that’s my educated guess," speculated Mike Wiles, the monument's chief of resource management.

During this exploration trip, volunteer cavers also discovered the deepest known point in the cave, measuring 814.3 feet. When measuring cave depth, measurements are taken from the highest point to the lowest in the cave, not necessarily from the surface.

To experience your own Jewel Cave adventure, the monument’s visitor center is open daily during the winter season from 8:30 a.m. to 4:30 p.m. Tours are offered Friday through Sunday; the Scenic Tour is available at 10 a.m. and 2 p.m., with accessible Discovery Talks at 9:05 a.m., 12:45 p.m., and 3:45 p.m.

Scenic Tour and Discovery Talk tickets are available on a first-come, first-served basis; advance ticket sales are not available during the winter months. For more information, contact the visitor center at 605-673-8300.