Place in the upper part of the city, near the Cathedral, the Castle of Ivrea (or "Castle with Red Towers") was built starting in 1358 by order of Amedeo VI of Savoy, designed by Ambrogio Cognon. To make way for the new building, which was to be built in a strategic position next to the most important centers of power (Bishop's Palace and the City), it was necessary to demolish several houses and part of the northern wall. The Castle has a quadrangular plant with cylindrical towers; the rooms are spread over three floors and overlooking the inner courtyard, with a well and an icebox. The access is by a drawbridge suspended over a moat. Along the perimeter of the walls, with battlements dovetail, runs the walkway, supported by defensive corbels. In the fifteenth century, the Castle became the residence of the Savoy, center of the cultural, artistic and mundane Ivrea. Between the sixteenth and seventeenth centuries, the Castle was restored and resumed its function as a military garrison. In 1676 a lightning caused the explosion of the ammunition depot in north-west tower (Torre Mastra) and several deaths. From 1700 to 1979 the building was used as a prison, undergoing many changes. The Castle, in concession to the City, can be visited on special occasions.