Kindergarten

"Kindergarten" first appeared in "On the Run". Kindergarten serves to create Gems with machines called Injectors.

Appearance
Kindergarten is a vast canyon. Numerous holes are carved from the rock faces; these are referred to as the "birthplaces" of many Gems, including Amethyst. Huge columns embedded with red gemstones protrude from the walls, and Injectors dot the landscape.

"Warp Tour"
Peridot mentions manually re-activating the Kindergarten, but is interrupted by a Flask Robonoid.

"On the Run"
Amethyst introduces Steven to this location. She reveals that she was made there, and that Gems used this place to create other "bad" Gems, or "parasites".

"Marble Madness"
The Crystal Gems follow one of Peridot's Plug Robonoids here. They stop her from reactivating it, at the cost of Peridot discovering the existence of Gems on Earth. Pearl mentions Kindergarten has been inactive for 6,000 years and would eventually destroy all life on Earth if activated.

"Keeping it Together"
The Crystal Gems go to the Kindergarten to search for Peridot. They find her, but she quickly escapes. Upon further investigation, Garnet discovers that Peridot wasn't trying to reactivate it, but instead she was checking on The Cluster, former Crystal Gems that Gem Homeworld shattered and forced to fuse, possibly as punishment for the rebellion.

Trivia

 * "Kindergarten" means "children's garden" in German and usually refers to a place of preschool education. In this case, it literally means a garden where children are grown.
 * It was destroyed by the incubated Gems around 6,000 years ago, as stated by Pearl in "Marble Madness".
 * The person-shaped holes on the sides of the Kindergarten, as well as the manner in which Amethyst slid into hers appear to be inspired by the Junji Ito horror manga, The Enigma of Amigara Fault.
 * Amethyst also has one of the few holes at ground level. The majority are raised a great distance off the ground and much closer to the other holes where Gems were made.
 * The body of the rig encases a structure that resembles an organic heart, which is attached to the head and feet via red and blue tubes resembling arteries and veins respectively.
 * It is unknown where or who the Gems were in the Kindergarten.