Gerald O'Neil and space travel

A plan already exists to build a city in space which could house several hundred thousand inhabitants and boast an environment identical to Earth's. This city is part of what will become a space colony orbiting the moon. The colony will have air and water, lakes and mountains. If this project becomes a reality, people born in the space colony can perhaps one day take a vacation on Earth.
The idea of creating a space colony where mankind could live in an artificial city was first proposed by Gerard K. O'Neil. O'Neil proposed the project soon after astronauts from the Apollo Project landed on the Moon in 1969. When scientists gathered together to the U.S. National Aeronautics and Space Administration to discuss O'Neil's plan, they decided the project was feasible and even came up with an idea about how the colony could be built. The scientists were influenced by the world population problem, then already topping 4 billion and estimated to reach over 30 billion within 100 years. The scie...