Abstract: A system for mobile robot localization, whose most remarkable feature is its extremely low cost, will be described in this paper. The paper focuses on the design of the prototype of the system, that is based on a laser emitter-receiver device, rotating continuously in a horizontal plane, so that the beam scans the whole environment. Several (at least three) mirrors are to be placed at known positions, fixed to the wall, at the same height of the rotating beam. Each mirror is arranged in such a way to make a so-called "corner cube", whose peculiar feature is to reflect the beam in the direction of incidence, so that the reflected beam can be caught by the receiver, which is coplanar with the emitter.. In this way the system can compute the angles at which the sensor "sees" each of the mirrors. A triangulation based algorithm has been developed to determine the position of the sensor with respect to a fixed reference frame in the environment. The sensor may then be placed on a mobile robot, so that the vehicle position in the environment can be computed.