The Lunar Sea Spire is an abandoned temple that was once an oasis for Gems on Earth, according to Pearl. It is currently at the bottom of the sea after Steven failed to restore it in the episode "Cheeseburger Backpack". However, it is shown in Attack the Light that despite its collapse, it is still habitable and can be navigated.
The Lunar Sea Spire was a free-standing tower structure in the middle of the ocean. Each consecutive floor was slightly smaller than the one before. At the top, there was a shrine to the Moon Goddess. When the Moon Goddess Statue returns to the pedestal, it repairs any damage to the structure. Gems used to gather at the Spire, but, in current times, the Spire has been abandoned. The Spire possessed an extreme gravitational pull that kept the waves from sinking it.
When the Crystal Gems visit the Spire with Steven, it is deteriorating and swarming with Crystal Shrimp. The Moon Goddess Statue is the one piece missing from the Spire that the Gems currently possess. The Moon Goddess Statue needs to sit on the pedestal at the top of the spire before midnight, or the entire spire would fall apart. Unfortunately, the temple sinks beneath the waves because Steven forgets the statue at home.
Pearl accidentally tells Steven that his mission to the Lunar Sea Spire was a test to assess his skills, stating that he had passed with a grade of at least 75 percent. She also mentions that the Spire should have been an even easier task, as it was in a much worse condition than the Gems had expected.
Schematics for the Lunar Sea Spire are seen on the Moon Base computer screen.
Centipeetle's drawing of her past shows a sketch of the Lunar Sea Spire, among other Gem structures.
While traveling around the world, Buddy Buddwick ends up at the Lunar Sea Spire as his second stop. While exploring inside it, he encounters the Crystal Shrimp and the Moon Goddess Statue.
The Lunar Sea Spire appears as the fourth world of Attack the Light, revealing that is still partially intact. It has four normal levels, two secret levels, a boss level, and a gauntlet level, for a total of eight levels. The enemies are all blue and include a puffer fish, sea star, angler fish, and jellyfish light monsters. The boss of this location is Blue Light, a whale. The theme song is Sunken Sea Spire.
- When the Spire began to sink, the ocean moved in similarly to how Lapis Lazuli's water tower collapsed in "Ocean Gem".
- Bismuth revealed spires are for the intellectuals of Gem society to think in.
- The magic or gem-powered mechanism sustaining the whirlpool below the spire is unknown.
- A concept map by Joe Johnston in Steven Universe: Art & Origins shows that the Spire is located in the northwestern Atlantic Ocean, between Newfoundland and the southern tip of Greenland.