Kindergarten

"Kindergarten" is a location mentioned in "Warp Tour" and is first shown in "On the Run."

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 massive machines Amethyst refers to as "Old Gem Junk" dot the landscape.

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

"On the Run"
Amethyst runs away with Steven to this location. She reveals that she was made here, 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 6000 years and would eventually destroy all life on Earth if active.

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.
 * Pearl implied that there are more Kindergartens.
 * 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 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 "Old Gem Junk" machines resemble bacteriophages: viruses that infect and reproduce within bacterium.
 * 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.
 * The pathogenic structure of the machines and their drill-like mechanisms suggest they are intended to unearth underground gemstones and infect them. Infection may transform these gemstones into the "bad" or "parasitic" Gems that Amethyst mentions.
 * In "Marble Madness," Peridot is implied to be in charge of the Kindergarten on Earth or the entire Kindergarten program.
 * In the same episode, Pearl says that the Kindergarten was damaged by the Gems that were incubated there.