Building multiuser interactive multimedia environments at Mitsubishi Electric Research Laboratories (MERL) is a highly interdisciplinary activity that involves the efforts of more than a dozen people. Our prototype systems involve expertise in computer graphics, animation, networking, artificial intelligence, human-computer interaction, computer vision, spoken language understanding, graphic design, learning theory, and drama. The relationship among the three areas of work at MERL discussed in this project report is a simple three-layer tier. At the bottom, supporting everything, are high-speed networks. On top of the networks we built a piece of middleware called the Scalable Platform for Interactive Environments, or Spline for short. Finally, Diamond Park is an experimental environment we are building using Spline.