The invention relates to a system for controlling access to a restricted area in a building, which system has a sliding door system and a controller for the sliding door system. The sliding door system has a door frame and a sliding door which can be displaced by a drive unit actuated by the controller. The door frame has a passage region and a wall shell region which accommodates the sliding door in the open position. The sliding door has an end face which points toward the passage region in the open position. The controller has a processor unit and a sensor unit, the sensor unit is arranged on the end face and the processor unit is arranged between the door leaves. A recognition device captures and checks credentials presented by a user. If the credentials are valid, a record is determined in a storage device, in which the credentials are assigned to an opening width (W) of the sliding door, in order to trigger the movement of the sliding door according to said opening width (W). The controller is designed to recognize a gesture made by the user and to actuate the sliding door depending on said gesture in deviation from the opening width (W).