Documentary buffs, grab the popcorn! We can’t wait to watch "10 Parks That Changed America," airing on PBS April 12. Host Geoffrey Baer will join historians, architects, and other experts—including The Trust for Public Land's Peter Harnik—for a look at the most influential city parks in American history. 

Can you guess which city parks made the cut? We think only a true green-space nerd could figure out all 10 using just these clues … 

1. This system of public squares was built into the original design for the city center. Thanks to the planners' foresight, visitors today are never more than a few blocks from a green space.

2. This park is among the earliest examples of an American city deliberately using green space to protect its water supply.

3. The word "cemetery" comes from the Greek for "sleeping place"—appropriate for this leafy burial ground, which doubles as a peaceful place to stroll or birdwatch. 

4. Intended to feel like a rural escape from a dense and bustling city, this park used to maintain its lawns with a flock of sheep (complete with shepherd). 

5. Designed by John Olmsted and Frederick Law Olmsted Jr., these parks included public bathing facilities for the working poor.

6. See the photo above. Might look like Europe, but it's far, far from it. 

7. Friends of this park won a U.S. Supreme Court case to stop a freeway expansion that would have cut it in half.
 
8. This precedent-setting park was the first to be built over a freeway. After a rough patch of problems with crime and abuse, upgrades and safety improvements helped give the space a second wind. 
 
9. When the plan for this park was first revealed, almost everyone hated it: even the family funding the project wanted their name removed. But the designer stayed true to his vision, camping out on the site in a sleeping bag and holding community meetings to win people over.
 
10. An early advocate for this innovative park has this to say about its debut:"One of the first things I noticed when I started coming up here was people holding hands. And this is not a hand-holding city."

Got some good guesses? Leave us a comment or send us an e-mail at blog@tpl.org—then tune in to PBS Tuesday for the reveal!