How to get to the center of downtown Paris from Charles De Gaulle international airport.
The fastest and cheapest way is by train.
Name of the Train: "RER B"
Cost: 10 Euros = 11 USD
Duration: 25-40 minutes (depending on how many stops)
Location: The lower level of the airport.
Picks you up: Multiple terminals in the airport.
Drops you off: Multiple stops throughout downtown Paris.
Purchase a train ticket from a machine for 10 Euro. They accept coins or credit/debit card. There are ATM's at some of the currency exchanges in the airport, it is hard to tell if they rip you off or not.