Though the caveman who discovered fire was heralded as a hero, the one who discovered ice was sentenced to sit on a bed made of it until it turned back into a drinkable form. Learn lessons from the Ice Age with today's Groupon to Polar Caves Park in Rumney, New Hampshire, opening for the season on Saturday, May 7. This Groupon expires on June 24. Choose between the following two options:

• For $5, you get one child's ticket for ages 4–10 (an $11 value).
• For $7, you get one adult ticket for ages 11 and older (a $15 value).

A natural doorway to the past, Polar Caves gives families an underground adventure through a network of caves and passageways formed by a retreating glacier during an age when woolly mammoths still roamed the earth. Encompassing a stretch near Hawk's Cliff, the highlight of Polar Caves Park is the caves themselves, which wind underground through the rock, twisting and turning before reemerging at the surface. Self-educating explorers can guide themselves through the subterranean walkways, where escaped slaves, Prohibition-era rumrunners, and angry teenage saber-toothed tigers found safety. Previous occupants have left behind evidence of their hidden lives, including a wood-burning stove and cider press. Along the trails, both above ground and underground, educational opportunities abound, with signs proclaiming local history and distinguishing local flora and fauna. Diminutive Dr. Dolittles enjoy practicing their deer whispering at the petting zoo, and landlocked fans flock to the birds at the waterfowl display.

Polar Caves Park is open seven days a week, 9 a.m. until 6 p.m.; crowd-lovers arrive between 11 a.m. and 2 p.m., and lone wolves prefer to come earlier or later. The main lodge's amenities include a gift shop and snack shop for bringing home memories that wouldn't fit inside a digital camera. Patrons can supply their own sustenance in the grill-plenty picnic area, and the park lends grill gear to families who left theirs in the driveway.

Polar Caves Park offers special rates on May 7 and 8; plan ahead to make sure you're redeeming your Groupon at the most opportune time.