(CNN)– Want to wander through Yellowstone, hike down into the Grand Canyon or spot alligators in the Everglades?

This coming week, forget the entrance fees.

The National Park Service will waive fees starting Saturday for National Park Week (April 16 to April 24).

Only a third of the 411 national park sites charge entrance fees, but they’re the biggies: places like Denali in Alaska, the Grand Canyon in Arizona and Zion in Utah.

The park service also turns 100 this year, and lots of celebratory events are scheduled.

Children can earn a junior ranger badge and take part in kids’ programs on Saturday, National Junior Ranger Day. Volunteers are welcome to help out in the parks on Earth Day, April 22.

The National Park Service’s online map lists the parks in every state.

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