Though certain outdoor sports translate well indoors, others prove unfit for smaller scales, as evidenced by the hot-tub 400-meter butterfly or downstairs-skiing slalom. Practice safe adventuring in an appropriate environment with today's Groupon: for $19, you get two all-day indoor rock-climbing passes (a $24 value; a $16 value for students), including shoe and harness rental (a $14 value) (up to a $38 total value), or two half-day kayak rentals (a $50 value) from River Sports Outfitters. Climbing will take place at The Climbing Center and kayaking trips depart from the Cove at Concord Park.

A seasoned purveyor of outdoor sporting equipment, River Sports Outfitters' adventure experts put gear to work on indoor climbing walls and local kayaking excursions. Rock-top scramblers suit up in provided harness and shoes at the climbing gym, lined with vertical slopes that impersonate cliff faces with gritty-textured walls, rocks in many shapes and sizes, and animatronic dancing mountain goats. Climbers of all skill levels can strengthen and stretch muscles on ascents up the tall rope-climbing wall, or free-climb on the shorter bouldering walls, which lose the rope and vertical ascent in favor of low routes that challenge spidery-men to master specific maneuvers and grips.

Half-day kayaking excursions launch boaters into the calm waters of the Cove at Concord Park, which is nestled within a 500-acre outdoor adventureland that brims with activities from biking to fishing and is backdropped by august groves of trees and manicured lawns. With a paddle, boat, and lifejacket provided, aquatic adventurers can leisurely explore the lake's scenic perimeter, or race ducks on figure-eight tracks through the lake.