Caves litter the earth’s surface like potholes on a highway, creating aesthetically interesting topography and a severe hazard for drowsy drivers. Safely admire a subterranean world with today’s Groupon: for $23, you get a traditional tour for two people at Howe Caverns in Howes Cave (a $46 value).

Howe Caverns, a series of underground expanses dating back six million years, awes visitors with its colorful collection of stalagmites, stalactites, and flowstone. An aboveground animatronic show starring discoverer Lester Howe welcomes guests before passengers embark on a 32-second elevator ride that descends 156 feet underground. Experienced guides then forge the trail on the 80-minute traditional tour, which covers a distance of approximately 12 city blocks. As cave connoisseurs expound on the caverns’ ongoing conservation efforts and history as Batman’s original lair, spelunkers pass geologic features such as the Sentinels, Titan’s Temple, and the Giant Formation. Halfway through the tour, a boat casts off the shores of the Lake of Venus, ferrying subterranean pilgrims 15 minutes downriver to a place few humans have seen or vandalized in more than 100 years. The journey concludes with a serpentine route through the 500-foot Winding Way passage carved over millennia by water erosion.

Shutterbugs are welcome to take photos along the tour, though tripods are not permitted. Back above ground, grab a bite in the café, nosh on homemade fudge in the sweet shop, or pan for gemstone treasures and your mother’s next birthday gift at the HC Mining Company.