The best was to get around Paris is to use the Metro or RER. The RER passes
thru the city center while the Metro has 13 lines and over 300 stations.
You have the option of buying single trip tickets or multi day cards
that allow unlimited travel on the Metro, RER, or bus system. Paris's
travel network is extensive and can be confusing. Be sure to pick
up a free transportation map at one of the Metro information desks.