Selene

Selene was the only natural satellite of Earth and the economic headquarters of the United Nations. Selene was also technically the largest city in history built by man, with one large city nearly covering the entire surface.

Geography
Selene is a very heavily populated moon made up of one city split into seperate sectors and districts. Before the Second Space Age, Selene was white viewed from Earth with thousands of visible craters that are now covered and repaired. It had little atmosphere, no oxygen, and very little water. After several terraforming attempts, however, Selene was mainly green, with only a few larger craters pocketing it's surface and a livable atmosphere. It had artificial gravity built deep inside it's core, making the gravity somewhat similar to that of Earth's. it also has several oxygen pumps that transfer oxygen onto the moon (however there is not that big of a need anymore as the Moon has it's own air now). Cities covered the entire surface of the moon save for it's poles, where water was stored and melted down for drinking water and sewege.

Political
Selene was the center of trade in Terran Space, with most business headquarters stationed there. It was a multilevel city with different kinds of culture on each floor depending on the area. In the upper sectors, most of the buildings were located on cliffs or hills, making mulilevels harder as they are built to appeal to upper class people and give them light and a good view.

The moon was split into twenty one different sectors all at different sizes depending on it's zone type. The Merchent Sectors are normally the busiest and most crowded parts of Selene, with nearly two billion civilians passing through them a week on average, however it have been much more.

It's residential sectors were more commonly beautiful, with millions of green park squares and gardens, depending on the area. The poorest sector was sector A, yet still being well into middle class. The richest sectors were Section C and the Limited Residence Zones (one home in the LRZ cost several million credits and up). There was also a zone where no residences or buildings were allowd known as The Lunar Forest Federal Park, where tourists could visit the first lunar forest on Selene and witness the pride of the United Nations Central Science Agency terraforming efforts, and the main source of natural oxygen on Selene. There was also a restricted zone known as Central Utility Administration Facility, which was managed by the Lunar Government. The capital district was the home of the Lunar Government, as well as several state and federal organizations and agencies, such as the Frederick Louis Faller Federal Science Agency Facility, Corporate Moderators Agency, Census Beareu of Selene, the Selene Security Force, and the Central for National Health Services.

There was also a small island in Lake Titanic where the Xelor Space Elevator (the tallest building in the UN (reaching past the atmosphere to the tip of space) which had been a space elevator until it's retirement in 2467 due to it's successor known as Space Cranes, however the island had been flooded by 2499. The only access to the Space Elevator was by the government's permission to conduct maintenance and ensure it's foundation was still sound.