Luna is the accepted multinational name of Earth’s only moon, which has many names in Earth languages. Luna was used by the Martians as a raiding base for taking human slaves, and they left a number of intact structures on the far side of Luna, which humans discovered and re-inhabited when they became capable of reaching Luna. Great artificial farms were renovated and adapted to Earth crops to feed the growing population.
Martian artifacts were found and studied, and through understanding of the underlying principles, many devices were created and refined. Most important were the various crystals used to enhance and control PSI abilities, which before this were elusive and almost unusable. The famous Luna University located here grew out of these scientific explorations and research units, one of most prestigious institutes of higher learning in the Solar System.
This complex is known as Luna City, and it has grown, with new structures built by Humans and Martians, as well as the various Galileani. Luna city is the only place near to Earth where Humans, Martians, and Galileani can meet and trade. The gravity is almost identical to that of the Galilean moons, and the Galileani have built huge flight cages to live in.
The Great Concourse of Luna City is famous for the availability of anything from anywhere. Great liners from Earth put in here, and hotels and restaurants have sprung up to serve the tourists. Luna City is the stepping off point for travel anywhere in the solar system.