The city of Sion and two hills overlooked by the castles of Valere and Tourbillon is a striking image . Both castles built between the thirteenth and fourteenth centuries , dominate the medieval old town of Sion.
The oldest, Valere, harmoniously blending style Romanesque to Gothic , houses the oldest playable organ in the world (1430) . Castle Valere obtained the rank of Minor Basilica during the visit of Pope John Paul II in 1984.
Tourbillon, defensive castle built in the late thirteenth century , was the summer residence of the Bishop of Sion. It was destroyed by a great fire in 1788 .
historic sites within the walls of the old town of Sion : the Chapel of All Saints (XIV ) and the Tower Wizards . Last vestige of the old fortifications of the city, it was a defensive tower at the northwest corner of the walls, built in the fourteenth century.