ditto on Chambord, to me the most monumental of all Loire chateaus - Villandry is nice for gardens but is not the finest interior - oh it's nice but not like Chambord or Chenonceau, the other most famous Loire castle.

No Villandry is not a great interior but I'm a gardener and adore the gardens so much I have visited it on two different trips.

Villandry for les jardins, bien sur!

In Paris garden lovers may want to visit the Jardin des Plantes next to Austerlitz train station - recently been rehabbed into a type of botanical gardens.

I've got the Jardin des Plantes on my list to visit next month. Hope it's not too late in the season.

Even last Christmas it was in bloom but should be fine earlier.

As for SMOG, Monday morning, followed by Sunday afternoon would be the best days for seeing things. The lack of cars on Saturday and Sunday reduces the smog levels and Monday morning, before the cars generate smog, is usually best. Friday and Saturday morning are usually the worst days for smog, as the cars continue putting out the pollutants, and they build up over the week. Once the generation of pollution slows on Friday, it takes a day or two for the levels to drop.

warmer weather IME like in summer makes the smog worse - folks with breathing problems may use caution - Paris I understand is hemmed in on many sides by hills that trap the pollution in a bowl.