On select days each year, America’s national parks and sites waive their entrance fees to allow all to enjoy nature at its finest. April 20 is the latest fee-free day across the country's national parks to kick off National Park Week, which runs from April 20–28.

National Park Week is an ideal time to head to popular parks such as Grand Canyon National Park or Canyonlands National Park, where special activities are held to celebrate.

Themed days occur throughout the week, including National Junior Day (when kids of all ages can earn junior ranger badges) and Transportation Tuesday, when you can learn about the transportation innovations that have helped visitors over the years experience the parks.

Sites will also be hosting individual events, including lessons on how to pitch your own tent at the Gateway National Recreation Area in New Jersey and Easter egg hunts and face painting at the Frederick Douglass National Historic Site in Washington, D.C.

Visitors can also take part in activities like painting with artists at Arches National Park in Utah, sunset hikes in Death Valley National Park, and spotting tadpoles and frogs and enjoying roasted marshmallows at the Chattahoochee River National Recreation Area in Georgia.

To get the most out of National Park Week, Will Shafroth, president of the National Park Foundation (the official charity of America's national parks) recommends calling local visitor centers to see if special activities are planned and to get tips on the best spots to avoid the crowds.

Shafroth also recommends keeping public or alternative transportation methods in mind if you’re not planning to travel by car, as nonprofit partners of parks like the Cuyahoga Valley Scenic Railroad will be operating rides around the park and from nearby cities.

Some of the lesser-known national parks Shafroth recommends visiting include Colorado's Black Canyon of the Gunnison National Park, noted for its rock climbing opportunities, and Arizona's Saguaro National Park, where visitors can see rare plants and animal species and enjoy 165 miles of trails dotted with wildflowers.

Finally, Shafroth suggests using the Find Your Park site to filter areas of interest by activities that range from biking and kayaking to children's programs to determine the areas you'd like to visit throughout the week.

And If you happen to be sharing your outdoor adventures during National Park Week on Twitter, use the #FindYourPark hashtag to unlock a fun ranger emoji.

This story originally appeared in Travel + Leisure.