La Roche-sur-Yon is a common Central West of France , prefecture of the department of the Vendée , located in the region of Pays de la Loire . Watered by Yon and its tributaries, the Riaillée and Ornay (and its tributary the Soivre), La Roche-sur-Yon owes its present appearance to Napoleon I er , which is a small town a modern city, based on a regular pentagon- shaped plan and endowed with imposing public buildings ( prefecture , town hall, theater, […]