Prefectures are usually located near the geographic centre of their departments; they were originally chosen for being within a day's travel on horseback from anywhere in the department. Therefore, the largest settlement in a department may not always be its prefecture: the department of Marne, for example, has its prefecture at Châlons-en-Champagne despite the city of Reims, near the Aisne border, being four times its size.
Prefectures are usually located near the geographic centre of their departments; they were originally chosen for being within a day's travel on horseback from anywhere in the department. Therefore, the largest settlement in a department may not always be its prefecture: the department of Marne, for example, has its prefecture at Châlons-en-Champagne despite the city of Reims, near the Aisne border being four times its size.