We present a description of a simulator of legged robots. The simulator allows the definition of different models of robots as well as different shapes for the ground. The robots are provided with many physical sensors (touch sensors in feet, inclinometers, and active camera, ...), virtual sensors (stability sensor, ...) and different motors that can be commanded either individually or coordinately. The controller of the robot is a separate module that the user can re-program at his convenience interfacing with the simulated robot as he would do with a real robot and without worrying about the internal structure of the simulator. Additionally, the simulator provides tools to monitor the workings of the robot controller: for instance it allows the drawing of traces for those mobile elements (body, feet, ...) that the user wants to monitor along time. As a last feature, the simulator includes the definition of landmarks identifiable with the robot camera (if they are at sight) and that can be useful to test navigation algorithms for legged robots.