If the Goonies and Indiana Jones taught us anything, it’s that “X” never marks the spot, and that subterranean treasure is notoriously hard to find. Spanish Cave, high on the eastern slopes of the Sangre de Cristo Mountains, is about to teach me the same hard lesson.

After driving my Jeep over a rough 4WD road to a trailhead, my caving partners and I set out on a Forest Service trail, turn onto an unofficial climber’s trail, and then peel off onto an even less recognizable caver’s trail that promptly disappears. We spend several hours navigating and bushwhacking through the forest to tree line.

Tired, we drop our packs to explore the surrounding terrain and scout a spot to camp. Searching for a spot to pitch a tent, I wander into a small gully where I feel a noticeable drop in temperature. Refrigerator-cold air rushes out of a three-foot-tall hole in the mountainside. Painted on the rock face next to the dark hollow is a pale, red cross. Spanish Cave.

Some legends die hard, and in the lore of Colorado’s lost treasures the legend of Spanish Cave is more persistent than most. Over the years—centuries, not decades—it has gone by many names: La Caverna del Oro, Marble Cave, and, most recently, Spanish Cave. Though its moniker has evolved, the fundamental details of its legend remain unchanged.

In the 17th century, Spanish conquistadors ventured up the Wet Mountain Valley and into the Sangre de Cristo Mountains. There they discovered Spanish Cave, and, deep within it, gold. Tons of it. The Spanish promptly enslaved a nearby band of American Indians and put them to work within the cave to mine its treasure. Shortly thereafter, the cave and its illustrious plunder fell into obscurity.

That was until a local newspaper report in 1919 publicized the rediscovery of the cave, complete with new and sensational details. A skeleton clad in Spanish armor lay chained in a pit inside the cave, an arrow piercing its rib cage. Deeper inside the grotto, a set of heavy oak doors barred passage to the shaft that led to the gold. Treasure hunters flocked to the cave, but if anyone ever found the treasure they kept it to themselves. By the 1950s and 1960s, experienced spelunkers journeyed to the cave, too—both to explore its inner reaches and to research the history of the legend.

Definitive evidence proving the details of the tale remains elusive, leaving many cavers skeptical. However, the history buff in me hoped the stories contained a bit of truth, and I resolved to explore the cave for myself. But I couldn’t do it alone. Spanish Cave’s precise location is a closely guarded secret among modern-day spelunkers, and it’s also technically challenging. At an altitude of just over 12,000 feet, it’s the highest-altitude, large limestone cave in the United States. And with a vertical relief of about 750 feet, it’s the deepest cave in Colorado, requiring rope work to rappel vertical drops, along with exposed scrambling in areas where a fall would be very bad. In short, it is one of the state’s most dangerous caves, and I needed chaperones. Fortunately, three members of the Northern Colorado Grotto of the National Speleological Society offered to take me into the recesses of Marble Mountain in search of Spanish gold.

The morning after our approach hike, we shoulder our ropes and set off from our camp in the gulch below the cave. We bypass the main entrance and continue upward to a second opening, where we will start our “through trip” from one end to the other. The upper entrance—an impossibly small hole in the ground at the base of a tall cliff—would not interest those with claustrophobia: It’s so small that my chest and back make simultaneous contact with the rock as I shimmy down into utter darkness. Then I rig my rappel gear on a rope that drops into an abyss. This is Frank’s Nasty Pit, a 150-foot free-hanging rappel into the bowels of the beast. When I’m partway down the rope, the walls of the cave bellow so far outward that my headlamp no longer illuminates them. The rope disappears into a pit of blackness, and I hang suspended in an inky night.

Touching down far below, I see piles of bones: mostly marmots, pikas, and other small animals that had wandered in and fallen to their deaths. As we continue on foot deeper into the cave, my partners describe place after place where cavers much more experienced than I have had their share of problems: Someone fell and broke his back here, another fell and broke his ankle there, yet another fell and broke her wrist over there. The idea of being down here, hurt and unable to call for help, is not one I cherish. The cave is cold—36 degrees or so—and damp, and puffs of condensation escape my mouth as my breathing quickens at the thought.

After more than four hours, we reach the Jug and the Pit. This is where early climbing parties reportedly saw the skeleton, and where treasure hunters from the early 20th century left behind relics like old hammers, rope ladders, and lanterns. Time has not been kind to the artifacts, which have disintegrated into nothingness. And so the legend remains.

We emerge out of the lower cave entrance into the blinding light of day as a thunderstorm rolls over the mountain. I didn’t see evidence of the Spaniards, or their gold. There were no oak doors, no skeletons. But significant portions of Spanish Cave remain unexplored and unmapped—only a small number of experienced cavers visit this place each year, and the cave’s inhospitable climate and technical nature make further exploration a difficult undertaking. It’s those distant reaches of the cavern that might hide the precious metal. It’s equally possible that the treasure is in another cave entirely. Littered with caves and limestone outcrops, this mountainside may still shelter long-lost treasure.

Of course, it’s just as likely that the treasure never existed. But that won’t stop people like me from dreaming. And it certainly won’t stop other cavers and treasure hunters from seeking out Spanish Cave, whether for its storied riches or for the thrill of exploring one of Colorado’s most challenging caves.

If You Go

To explore the caves of Marble Mountain, begin at the Rainbow Trailhead on South Colony Road, southwest of Westcliffe. Only the first 40 feet of Spanish Cave’s lower entrance are safe for novice cavers. Don’t go beyond that point without experienced caving partners. If the call of the cave is too much to bear, try contacting area cavers who can show you the underground ropes. If your caving skills aren’t up to the challenge of Spanish or you can’t find a chaperone, nearby Burns Cave (downhill from Spanish), Bridal Cave (with a 10-foot-tall entrance), and White Marble Halls (with its name painted on the rock near the entrance) are all friendlier alternatives and are accessible from the Rainbow Trailhead.

Peter Bronski is a regular contributor to 5280. E-mail him at letters@5280.com.