Terrasphere

A terrasphere was a simulator constructed by the Undine in 2734. They were designed to mimic the atmosphere and conditions of Starfleet Headquarters, located on Earth. They were utilized by the Undine as a way to train themselves to get used to the conditions that humans and the Federation lived in. These were ultimately useful for the Undine when they began the infiltration of the Federation and Starfleet by manipulating their forms to match those of Starfleet officers, usually high-ranking with some power on their side.