Squinty-eyed cave critters navigate deep darkness with a host of adaptations, feeling their way through caverns with improved hearing and buddy systems with lantern-bedecked eels. Survey artificially illuminated subterranean shelters with today's Groupon: for $15, you get two tickets to a guided cave tour and a souvenir gift pack (up to a $31 value) from Indian Echo Caverns in Hummelstown.

Indian Echo Caverns' trained trekkers shepherd patrons around ancient stalactite-packed caverns, unloading an arsenal of anecdotes about early occupants of the cliff crevices. Scout nine rooms of Susquehannock Native American stomping grounds, still emblazoned with cave drawings of native inhabitants' favorite comic strips, while tour guides tell tyke-friendly tales of the Mystery Box and cave-dwelling Pennsylvania Hermit. Opened to the public in 1929, the flowstone factory houses a swarm of breathtaking structures etched over 440 million years, including stalagmites, columns, and lakes. Subterranean travelers identify a wealth of indigenous wildlife, from the flap of cave bats to the soulful gurgles of blind fish-blues musicians. Though not included in today's Groupon, pint-sized prospectors can pan for amethyst at cavern-adjacent Gem Mill Junction or poke an Indian Echo goat at the petting barnyard.

Located only five minutes from the chief chocolatiers at Hershey, Indian Echo Caverns gives guests their own version of a sweet ending with a gift pack (a $5 value), including a logo pen, magnet, and more. Procure additional keepsakes from the spacious gift shop, with shelves stocked with souvenirs, Native American artwork, and pet cave rocks.

Reviews

Ten Yahoo! Travelers award Indian Echo Caverns a four-star average. Seven Insider Pagers also give Indian Echo Caverns a four-star average. Seven Yelpers give it a 3.5-star average.

• The caverns themselves are gorgeous and well worth the trip – Kimberley Z., Insider Pages
• The tour was informative but also had some stories thrown in for children to enjoy. – Sara A., Yelp, 7/7/10