The departmental seat of government is known as the prefecture ("préfecture") or "chef-lieu de département" and is generally a town of some importance roughly at the geographical centre of the department. This was determined according to the time taken to travel on horseback from the periphery of the department. The goal was for the prefecture to be accessible on horseback from any town in the department within 24 hours. The prefecture is not necessarily the largest city in the department: for instance, in Saône-et-Loire department the capital is Mâcon, but the largest city is Chalon-sur-Saône. Departments may be divided into arrondissements. The capital of an arrondissement is called a subprefecture ("sous-préfecture") or "chef-lieu d'arrondissement".