This paper describes the architecture, capabilities and implementation of The Clockworks, an object-oriented modeling and visualization system that encompasses a wide variety of modeling, image synthesis, animation, programming and simulation capabilities in a single integrated environment. The object-oriented features of The Clockworks are implemented in portable C under UNIX using a programming discipline. These features include objects with methods and instance variables, class hierarchies, inheritance, instantiation, and message passing. The initial goal of our work was to create a set of integrated tools to assist both engineers and artists in the creation of synthetic images and computer animation. Several important requirements were defined early in the project. First, the system would not be designed for a specific application; we wanted to build generic tools in a bottom-up fashion. Second, the architecture of the system would be general enough to support both interactive facilities and the importation of data from external sources. Third, the system had to be portable in order to adapt to our ever-changing computer facilities. The work that followed has produced more than 100,000 lines of C, which is now known as The Clockworks.