The Sim Zone was officially considered part of i/o originally (at least with the maps putting it as one section). Later maps showed the two separate though and you always had to enter it through the hallway, not through the rest of i/o which was separated by a glass wall.
From COSI's 2004 website: "One of the most effective ways for people to learn is to use objects that are already familiar and interesting to people. The Sim Zone (short for Simulation Zone) uses video games, a very common and popular technology, and other simulations to teach the development of computers, thereby making the Sim Zone an ideal complement to the i|o exhibition area. It is dedicated to the preservation of arcade game history, the celebration of learning through social interaction, and the pursuit of the coolest new game technology the industry has to offer."
The Sim Zone had a motion simulator and an arcade showing the history of games. The gaming and motion simulator originally needed to be paid for separately but later became free. The Sim Zone was closed and Space moved to its location around 2004.
Below is a map made in either 2003 or 2004.