The Loire is not only a region, it's a river:
And it's because of this river than there are fertile soils and a micro-climate. The Loire is known to the French as "the garden of France" because of its beautiful landscapes, its numerous agricultural products, its cheese and its wine!
If you only have one day to spare in your program to go see the Loire chateaux, it can easily be done but it will be a long day (that means that it's going to cost you). We need 12 hours. Expect a departure at 8:30 AM from your hotel. After a 2h30 drive, except a short stop for toilet (and coffee!) if necessary, the first stop for sightseeing will be at 11 AM when we arrive at the chateau of Chambord:
If we go in, you'll want to visit Leonardo da Vinci's tomb (no less) inside the Chapel Saint-Hubert
(which we'll see from the outside anyway):
Otherwise, a place that you'll really like at Amboise (500 yards from the chateau) is the Clos-Lucé,
Leonardo da Vinci's last know adress where he lived his last 3 years. Not only is it a beautiful house:
You will also find life-size replicas of his inventions in the delighful park which is full of surprises:
But the highlight of the day will be the visit of the chateau of Chenonceau which, on its own, is totally worth the trip:
Then we will drive back to Paris. I recommend that we have a quick (but decent) lunch on that day (to save time) and we should be back around 8:30 PM after a 2h45 ride back (I make great conversation or, chances are, I'll let you sleep) for you to have "late" dinner in Paris. Or we can have a nice dinner in Chartres on the way back so that you can see the illuminations which are really worthwhile. We can play it by ear. I'm flexible (but I will charge you for the extra hours of course). In any case, it will be a great day!
where we can visit the chateau (or not).
but you will also find there excellent copies of his best works:
Tank (notice the canons sticking out at the bottom)
and you'll see models of his inventions made from the notes on his manuscripts (great for your kids or grandkids):
You can see Mona better than at the Louvre!