There's nothing much left from the medieval castle built on a rocky spur overlooking the Vienne river, one of the tributaries of the Loire, but the big clock tower is still imposing and it's a landmark in the local scenery. Chinon can easily be included in a 2-day trip but difficultly in a one-day trip. I wouldn't put it at the top of your list though, but it's an option. Here below are a few pics: