We present a novel algorithm for navigating a large number of independent agents in complex and dynamic environments. We compute adaptive roadmaps to perform global path planning for each agent simultaneously. We take into account dynamic obstacles and inter-agents interaction forces to continuously update the roadmap by using a physically-based agent dynamics simulator. We also introduce the notion of 'link bands' for resolving collisions among multiple agents. We present efficient techniques to compute the guiding path forces and perform lazy updates to the roadmap. In practice, our algorithm can perform real-time navigation of hundreds and thousands of human agents in indoor and outdoor scenes.