We had 4 days in Paris last time we went to Eunrope.You'll love it. Make sure you prebuy entry tickets to the places you want to see -  e.g the Eiffel Tower or the Louvre - before you leave australia. That way you won't spend hours (literally) queueing. Also, for getting around have a look at hop on hop off day or two day tickets on the batobus - a river bus that does a round trip on the Seine.

We queued for the Eiffel Tower at 6pm on a winter Sunday evening, took forever and brrr. They only had one entry/lift open at that time of the day.

I liked the Palace of Versaille.. again it was winter there so gardens not a feature as they would be in spring. You can pay a little extra and go to Marie-Antoinettes estate at the rear of the grounds. It has only been open to the public since 2005.

That should be 2006 ^^.

The fountains weren't going when we went to the Palace on a week day, as they were only operating in the weekends at that time.

Museums  are closed on Monday's in a lot of places in Europe. The Louvre is closed on Tuesdays.