Here are the directions to get from Paris Montparnasse station to Versailles Chantiers in less than 15 minutes on the train (there is a 10-20 minute walk from the station to the château). Tell me if some parts are not clear. The train schedule is on the web page I created. Go to: http://inside.urbanschool.org/~alew/versailles to find out how to get to Versailles in 12 minutes (minimum time) on the Express train.

It would be interesting to see if that train saves the <i>average</i> visitor any time. If I were staying anywhere near RER C, I don't think I'd mess with getting to Montparnasse, waiting an average of 30 minutes (the trains run about an hour apart), and walking twice as far to the chateau just to save a few minutes enroute.

If one is already fairly close to Montparnasse, I suppose it would work, but I think the determining factor should be: are you closer (in time) to Montparnasse or the RER? Most people I think fit the latter category.

Robespierre, that is true. I lived near Montparnasse and it was much easier for me to go via Versailles Chantiers instead of taking the 40 minute RER ride. I used to board the trains 1 minute before they left on the TER from Montparnasse, which I do not recommend doing. Llast year the RER closed off the section between Invalides and Saint Michel, which caused a big inconvenience for taking the RER C to Versailles Rive Gauche station.

Is that section still closed?

No, the RER C section between Saint Michel and Invalides is currently open. It will be posted at http://idf.sncf.com/FR/ if there was a closure of a section due to construction.