What's an Easter Egg? It's a hidden surprise in a video game, movie, or location that's added to be discovered by those in the know.

Hollywood has been adding easter eggs in movies for years, including The Godfather's legendary use of oranges to indicate a character that's soon to die, or Stan Lee adding himself to each Marvel movie. The City of Oakland has some well known easter eggs too, including the Gnomes of Lake Merritt and monuments of Joaquin Miller Park.

Oakland Zoo has its fair share of hidden easter eggs too -- locations or things that make you stop and go "Whaaaa's that?" or "I never knew!"

Here's a key to discover some of our favorite hidden gems, solidifying your status as an Oakland Zoo insider:

Is it a gate to another dimension? The entrance to a mine? Asubterranean pathway to the bay? Nope -- the dark allure of this hobbit hole, located between the train tracks and lower tiger deck, is actually a relic of older days at the Zoo. In the mid-20th century, Oakland Zoo sported a state-of-the-art primate habitat at the entrance of the park. This towering 50'+ primate habitat, with its classic Space Needle silhouette, was only accessible via an underground tunnel via this odd-looking gate.

While the above-ground structures may be history, this gate acts as a reminder of our history, not to mention the lengths our animal care staff go to care for our animals - that tunnel looks scary as heck! These days, it's an access point for the flamingo moat.

If you weren't aware, you can find a branch of the LittleFreeLibrary in the Children Zoo's Edna Mack Butterfly Garden. Take a book, return a book, and continue this sweet tradition of sharing the gift of word.

What's cooler than a dinosaur? How about a prehistoric "SuperCroc" that ate dinosaurs for lunch? Meet Sarcosuchus imperator.

Located across from the Reptile and Amphibian Discovery Room, this ancient dinosaur grew up to 42 feet long and lived in Africa 110 million years ago. These days, the closest we get to giants like this are Ash, Roosevelt, and Bismark, our trio of American alligators that continue on, showcasing Sarcosuchus imperator's physical dominance.

Next time you're on the Children Zoo pathways, keep your eyes to the ground in search of creepy crawlies or test your animal tracking skills. While designing the Children Zoo, our architects added some extra flare, honoring the future inhabitants of their efforts. As you walk the pathways, keep on the look out for lines of leaf-cutter ants or Aldabra tortoise footprints around each corner.

Each spring, the Children Zoo's lily pond becomes a breeding ground for the native Pacific chorus frog. Their loud songs fill the Children Zoo and provide a reminder to guests and staff alike that warmer weather is on the horizon!

Let us know if we missed any of your favorite hidden easter eggs around the Oakland Zoo by reaching out to web@oaklandzoo.org.