Great Sand Dunes National Park and PreserveLocation: Southern Colorado
Known for: Its land-locked towering sand dunes
Biggest crowds: June through August
Accessibility: The road only goes from the park entrance to the visitor center; you'll want to walk or hike the dunes.
Why kids like it: They can play in the sand, build sand castles, and slide down the dunes on saucers.
What hikers say: Climb the High Dune for the most scenic view of the dunes; walk in the Preserve to trek on wooded trails to a fabulous view of 13,000-foot mountains.
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Mesa Verde National ParkLocation: Southwestern Colorado
Known for: Hundreds of ancestral Puebloan cliff dwellings.
Biggest crowds: Mid-June through August
Accessibility: You can see some of the park from scenic road overlooks, but taking a guided hike is your best bet.
Why kids like it: You don't see clusters of ancient stone houses on cliffs every day!
What hikers say: Be aware that hiking is restricted, and you're sometimes required to have a ranger as a guide.
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Rocky Mountain National ParkLocation: North-central Colorado
Known for: Alpine lakes and scenic peaks.
Biggest crowds: Summer
Accessibility: The park's shuttle will take you to the main sites.
Why kids like it: There are elk everywhere.
What hikers say: Remember to pace yourself, since you're at a higher elevation—but the views are definitely worth it.
Best for:Visit the Travel Talk forums for help on planning your trip