Suggestions for activities in Tours

I assume you're going to visit the surrounding Chateaux. Think about taking a bus trip to Loches. Not many people go there but it's one of the amazing unseen jewels of the Loire Valley. Also a city bus takes you from the train station to Villandry. For other chateaux there's a company that runs to the chateaux called le Quart de Tours. They simply get you to the chateaux. You pay once you're there, but it's a fine way to get to some ones that are difficult to get to via public transportation.
Tours is fantastic. The Beaux-Arts museum is amazing and it's right next to one of my favorite cathedrals in France, St. Gatien.
There's also
-The Basilica St-Martin
-Hotel Gouin
-Le jardin Botanique

If you go in the summer there's an amazing Guinguette on the Loire where you can have a few drinks and enjoy the scenery at night. Plus the historic Place Plumereau is an unforgettable place to have lunch and soak in the old city.

I have lived in Tours for college and try to go back every 2 years or so. It feels like a homecoming every time.

As the previous poster observed, Tours is right in the middle of Loire Valley chateau country. Google a map of "Loire Valley chateaux" and/or refer to the RS guide for France to get nice descriptions of the various chateaux and see how near/far they are from Tours. Personally I wish I could spend a month visiting one after another!

Rick Steves also has a TV show about the chateaux on this site at << https://www.ricksteves.com/watch-read-listen/video/tv-show/season-8/frances-loire-chateau-country >>

I second the suggestion of Loches. Not a big grand palace like Chambord or Chenonceaux but what's left of a walled medieval city, including a church with some Roman sculpture, an intact smaller Renaissance chateau with strong historic associations, and the ruins of a big medieval keep. In a pleasant town. If there's an easy connection to Tours so much the better.