Montparnasse station is served by 4 metro lines (no RER station) and 10 bus lines. If you are not in a hurry, it is an economical solution to reach the major stations and high places in Paris but:
- take into account very long connecting corridors ,
- only line 4 will take you directly to the east and north stations for around 40 minutes,
- to reach Paris airports via the RER, you will have to go through Châtelet-les Halles , a sprawling station if there is one, or rely on shuttles by bus but with transport time of at least 1 hour.