Our base for visiting the Loire Valley was in Blois - or rather just across the river from Blois. This region of France is famous for the large number of chateaus including the one that dominates the skyline of Blois.
The chateau at Blois has a lumieres program at night. It's not as impressive as Chartres but it's still interesting. You buy tickets and go into a courtyard where there are projections on all four interior walls. You need a headset to hear the stories being told (with many languages available) so bring earbuds if you have them, if not you can buy them for a couple Euros extra. Some of the lighting effects are pretty impressive.
Just a bit south of Blois is Cheverny which is a privately owned but visitable chateau. The grounds here includes the chateau, an orangerie turned restaurant and some garden areas.
Down river from Blois, almost to the city of Tours is Amboise. Amboise has multiple chateaus including one where Leonardo da Vinci lived and the main Amboise chateau which dominates the center of town.
Amboise is a lively walkable town with many shops and restaurants. The town overlooks the Loire which is very shallow here as it is in many places above Tours. The Loire is not generally navigable. The drive here from Blois can be done along either bank of the river but on the south side you'll pass several smaller chateaus as well.
Probably the two most visited chateau in the region are Chambord (east of Blois) and Chenonceau (south of Amboise). We didn't visit Chambord due to chateau fatigue but we did go to Chenonceau. From a distance, approached on land it doesn't look all that distinctive. There are several formal gardens surrounding it.
Up close, it is quite distinctive. Chenonceau started as a toll bridge on the Cher river (a Loire tributary). It later became a toll bridge with fortifications. The bridge was enclosed into a hall, a gallery was added on top of that and it ended up like this. Boats can pass underneath it still and the kitchens are located at water level in the main pilings so that food deliveries could be made by boat.
There's quite a lot to see at Chenonceau besides the castle (which involves a nice self-tour). Along with the gardens and a small maze there is a restored village area, a museum of sorts chronicling the history of horse-drawn carts, an enormous vegetable and flower garden and several restaurants.