Doorway (MissFitt)

The Doorway is a name given to a rift in space-time located deep within the walls of the crater of Olympus Mons on Mars. It is where one can observe or rapidly travel to one of several places in this universe as well as alternate realities.

History
It is unknown how the rift that would become the Doorway came to be. The mystical Order of the Obsidian discovered it thousands of ago when they were seeking a place of solitude where they could acquire the knowledge of the meaning of existence. Due to its highly unpredictable nature and the potential danger it may pose, the Obsidians kept the rift a secret and built their sanctuary over it in order to keep it hidden. They were especially committed to keep this site hidden from the Great Diamond Authority, due to the implications it could have for rapidly expanding the Gem Empire in this world and into other dimensions.

After the Rebellion on Earth, the Order of the Obsidian was all but destroyed in retaliation for their role in aiding the Crystal Gems. Its members, though all except Obsidian lost their lives, fought and managed to conceal the Doorway from Homeworld, and even long after the place and order were forgotten Obsidian continues to stand as its solitary sentinel to this day.

Properties
The Doorway is one of several portals (or wormholes) that connects to far distant points in this universe as well as alternate realities. Of the ones located in this universe, it is the one nearest to any place the Gems are aware of and travelled to, and certainly the closest to Earth Though it is connected to other wormholes, the place it leads to randomly changes over time. For instance, if two people were to enter it in succession, regardless of the time between them, chances are they will end up at different places or different dimensions. This is not guaranteed though.

In addition, the Doorway can also serve as a window, merely allowing others to view into it. According to Obsidian, it shows multitudes of worlds simultaneously, and it takes a highly trained mind to pinpoint a desired location to observe.

Trivia

 * Olympus Mons is an extinct volcano located on the planet Mars. It is the largest mountain in the known Solar System.