The elevator system includes an elevator hoistway bounded by a surrounding structure, two or more entrances to the elevator hoistway, guide rails, which are fitted into the elevator hoistway and also an elevator car with door(s), which elevator car is configured to be movable in the elevator hoistway between the aforementioned entrances to the elevator hoistway along a vertical trajectory determined by the guide rails. Each entrance to the elevator hoistway may be bounded by a door frame, onto which a hoistway door is fitted. The door opening of the elevator car may be bounded by a door frame, onto which the car door is fitted. The elevator system includes for each entrance to the elevator hoistway a marking piece fixed immovably to the frame of the hoistway door, wherein the marking piece indicates the location in the elevator hoistway of the entrance to the elevator hoistway. The elevator system may also include a reader moving along with the elevator car, wherein the reader may be fixed immovably to a fixing point on the frame of the car door and may be configured to read the marking piece.