Brick-and-mortar interactive science centers offer fun and educational experiences for visitors of every age. But in a virtual world, many of the constraints of the real world can be overcome, offering experiences that transcend reality. Exploratorium staff members have created just such a space in the massively multi-user, three-dimensional world of Second Life. In the virtual museum called the 'Splo, weíve been experimenting with the social, contextual, and educational possibilities of a world in which people can fly through the solar system, scan their own bodies, and change gravity so they can bounce off walls. In mixed-reality events which combine live media programs with the virtual world, visitors can watch a solar eclipse while sitting next to someone on the other side of the earth. What does this mean for other museums interested in creating their own virtual environments? In this paper, we share our own experiences, and offer some thoughts and recommendations.