Biosphere2 is the largest closed dome research facility ever attempted. Built in the 1990s as an experiment at living on Mars. Despite many issues, the project had many breakthroughs, such as the psychological problems of teams in close proximity, the limited ability to grow sufficient food, the destructive ability of insects and the nature of concrete to eat O2 and generate CO2. 7 people lived inside for 2 years. The project, outside Tuscon, eventually dissolved and is part of U of Arizona.