The Reef used to be a frequently used structure, specifically made for the use of Pearl creation, repair, and modification. The structure is equipped with an artificial intelligence named Shell, which assists the user in activating the building's functions. It was later deactivated by Steven and Mega Pearl within the episode in "Volleyball".
The Reef has an ocean motif. The building is shaped like a clamshell and it is located on an island in the middle of an ocean. Outside the building's door is a bridge, that connects the island to an unknown piece of land. On the inside, it includes, but is not limited to, an activation room (as shown when Steven places his hand on a Gem pedestal), a Pearl "remodeling" room, and a Pearl repair room.
Shell, The Reef's built-in A.I., is a helpful guide that makes suggestions as visitors travel throughout the structure. After Pearl and Pink Pearl's argument and Steven's outburst, Shell decides that the two Pearls are far too "broken" to be repaired and require rejuvenation, trapping them in a shell and sending shockwaves throughout their bodies. This leads to the two having a heart-to-heart and Pink Pearl acknowledging her trauma; this combined with the attempted rejuvenation causes them to fuse into Mega Pearl. Shell is voiced by Deedee Magno Hall.
The Reef was created a long time ago in order to create Pearls, in an unknown process. It was used for many years, creating an unknown amount of Pearls. After the beginning of Era 3 however, it was shut down due to Pearls no longer being made.
The Reef made its first and only appearance, acting as the main setting of the episode. It is later destroyed by Mega Pearl with Steven's help.
- Although it is never stated within the show, Rebecca Sugar has stated that White Diamond is involved with the creation of Pearls.
- It was later revealed that the Reef was created as part of White Diamond's fifth conquered planet.
- The clamshell-like design of the building and the fact that it is surrounded by ocean mirrors how Pearls are created in real life (from oysters and other mollusks found in the ocean).
- The seemingly peaceful A.I. that turns out to be "evil and murderous" in the end, along with the walls forming in the objectification hallway and Mega Pearl having to create a series of "holes" on said walls for Steven to pass through, maybe a reference to the video game Portal. This is further evidenced by the fact that Shell's name is extremely similar to that of the protagonist of Portal, Chell.
- The overall interior design of the building is a homage to the Art Nouveau style of architecture, which was the prevailing movement of applied arts during the late 1800s to 1910s and is characterized by the use of organic forms, most notably sinuous lines (also known as Whiplash Curves) to create elaborate and intricate designs that mimic nature. Specifically, the interior design of the building takes inspiration from Casa Batlló, a residential apartment designed by Catalan Modernisme architect Antoni Gaudí.
- The planet the Reef is located nearby may possibly be Saturn, as Jupiter is seen just before arrival at the Reef, and a gas giant with a large ring can be seen in the background. Additionally, this could mean that the "planet" the Reef is located on could be Titan, one of Saturn's moons which has an ocean.