In this paper we study the technologies that are available for interactive and cooperative 3D environments. In particular, we describe how state-of-the art videogame 3D engines can be fruitfully used to create interactive 3D worlds that leverage on the photorealistic quality of the graphics and the high level of immersive navigation. We provide, first, a categorization of videogame 3D engines from the point of view of their usage in creating interactive 3D worlds and show a comparison of the most important characteristics. Then, we show an example of how we used a commercial videogame engine to create an interactive an enjoyable visit to an archaeological site.