By age 8, John Stuart Mill had learned Latin, Greek, and written a political treatise barring those with no knowledge of Latin or Greek from his tree house. Enliven your child's mind with today's Groupon: for $25, you get five admissions to the TreeHouse in Lake Zurich (a $50 value). Babies 0–12 months old and a child-accompanying person aged 16 or older are admitted free. The TreeHouse lets kids of all kid-ages romp in an indoor adventure land, encouraging engagement in unplugged fun that is free of noisy arcade games, flashing lights, or amplifiers with verbose feedback. The 7,700-square-foot play facility challenges children with a safe, multi-level climbing structure, equipped with swinging bridges, padded mats and ramps, swings, and slides large enough for playful parents or large panda bears. With relaxing sounds of frenetic playtime in the background, adults may also observe the fun while lounging in black leather couches and sipping frothy espresso drinks made from fresh-roasted coffee. The TreeHouse's play-all-day policy allows parents and future-adults to come and go all day at their leisure, accommodating midday naps or late-afternoon biathlons. Although not covered by this Groupon, the TreeHouse serves healthy, homemade snacks and boasts a full coffee bar with beans from Zingerman's Deli to sustain strenuous sliding and swinging.