The United City is the first residential plant that was built outside of the Earth’s atmosphere. It is located in the east pole of the Mars, which is the fourth planet from the Sun. It has a total living area of 0.9 km2. The United City project was first launched in 1990, and finished construction in 2008.

The prevention of extinction of human race is the primary intention of the United City project. A Mayan prediction had been found in the Mayan historical remains in Mexico during June, 1989 that indicated that December 21st, 2012 would be the doomsday. The majority of the society and governments around the world believed this prediction because of the previous Mayan predictions had been proven to be very accurate.

The concern of extinction of human race rose after the Mayan prediction of doomsday. On December 20th, 1990, leading by the United States, many countries including Japan, China, Russia, UK, and Germany announced to launch a project to build a city on the Mars. The projected duration of construction of the city would last over 15 years. The cost of the project is over 37 trillions. The primary fund sources are from the US, Japan, China and UK governments. The DPA (Doomsday Prevention Association) which consisted over 300 scientists from more than 30 countries was founded to provide technology support for the United City project.  Over 150 space workers were sent to the Mars to build this project. They were also the first group of human beings to test the possibility of living on the Mars. 

On June 1st, 2008, the president of the United States announced the completion of construction of the United City. The United City can hold a capacity of up to 1000 residents. Due to the lack of oil, solar energy is the main power source for the entire city. Solar power is only allowed to be used for survival purpose, such as air filtering and food growing. Small amount of liquid stage water has been found from underground to supply for 1000 people’s use for up to one year. Glacier which could be used to transform into water for emergency use, was found in both North and South Pole of the Mars. People living in the United City must wear a special mask in order to convert the Mars’ CO2 based atmosphere into oxygen. In order to offset the reduced gravity on the Mars, one must wear clothes that are made from materials that are ten times heavier than regular nylon.

A total number of 963 people were sent to the United City prior to the official doomsday. On Jan 1st, 2013, the United Nation declared that the Mayan prediction of doomsday was a mistake. Residents on the United City started their return after the declaration. The last group of residents arrived on Earth on Mar 15th. Out of 963 people, 951 people survived during the immigration and return. It successfully proved the possibility of living on the Mars.

The United City becomes a space lab that scientists can stay there to do future development. The DPA was working to develop long term strategy to make the United City a better living environment. On May 2nd, 2013, the United States permits space travel to the United City. As of June 12, 2013, more than 200 people signed up for the space travel.