Services are provided by service buildings; access to these buildings has evolved through the games. In the first few games, services were distributed by zone of effect, with access determined entirely by absolute distance to the facility. In later games, a service building employs a "walker". The walker will leave the service building and walk along connected roads, taking a random direction at every intersection. Eventually the walker will return to the service building directly, and the activity will repeat. As of Caesar IV, this was changed to a walking distance measure, whereby access is determined by the distance to the building following the roads; actual distance is irrelevant if the shortest route by road is still too long.