This paper presents the simulation techniques that are available in Metropolis, an inter-disciplinary research project that develops a design methodology, supported by a comprehensive design environment and tool set, for embedded systems. System behavior is non-deterministic in general, especially in the beginning of the design process, when several key decision, such as the mapping on an implementation platform, have not yet been made, and thus the traces obtainable by simulation are not unique even under the same input sequence. One may want to visit as many traces as possible for regression tests at the final stage of designs, or may just need one valid trace for a quick validation of the design at an early stage. Our techniques can adapt to these different objectives easily. They are also platform-independent in that simulation using different languages, such as SystemC 2.0, Java, and C++ with a thread library, are possible. This feature is important for co-simulation between designs captured in Metropolis and those that have been already designed in other languages.