The U.S. National Park Service is offering free admission to all national parks in celebration of National Park Week from Saturday, April 21 until Sunday, April 29.
All of the nearly 400 parks, preserves, monuments, recreation areas and historic sites in the system will be free of charge.
While you're there, the Park Service wants you to snap a photo of yourself and post it to their website.
Every U.S. state except Delaware has at least one national park. There are as many as 25 of these sites available throughout California.