Whether you take the Metro, the bus or the RER suburban trains, the whole city is very well covered. The Metro is probably the best way to get from A to B, while you’ll see more of the city if you travel by bus. There are various ticket options so you should easily find one that suits your stay. The best place to buy them is in any of the Metro and RER stations. Alternatively, rent a Vélib' bike for the day and explore the city on two wheels.