We are planning on taking the RER-C to Orly south. My question is does anyone know what number we should take and which stop to get off at? I don't have a good map that shows me this. I know there are various numbers to the same line. Any help will be appreciated!

http://www.fodors.com/miniguides/mgr...ur_section=tra

"By Train: From Roissy Charles de Gaulle airport, the least expensive way to get into Paris is on the RER (Réseau Express Régional, or Regional Express Network), the suburban commuter train. Each airport terminal has an exit where the free RER shuttle bus (a white and yellow bus with the letters ADP in gray) passes every 7-15 minutes to take you on the short ride to the nearby RER B-line station: Terminal 2A (exit A8), Terminal 2C (exit C8), Terminal 2B (exit B6), Terminal 2D (exit D6), Terminal 2F (exit 2.08). Trains to central Paris (Les Halles, St-Michel, Luxembourg) depart every 15 minutes. The fare (including métro connection) is EUR7.62, and journey time is about 30 minutes. Note that you will have to carry your luggage down to the train tracks, and trains will be crowded if you are traveling during rush hour."

Other Orly transfer options (shuttles, etc.) are also provided at this link.

I did go to the website you suggested. However, it doesn't offer me anymore information than everywhere else I have looked. I have seen RER-C 2,or 3, or 4...I'm just not sure which goes to Orly.

Have you checked out this map? http://www.paris.org/Metro/gifs/rer01.map.jpg
RER C is everything that is in yellow, RER C2 is the closest to Orly. Get off at Antony and take the fully automatic Orlyval train to Orly Sud (via Orly West).
There's a good map on http://www.citefutee.com/orienter/rer.php# as well.

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