An essential part our Paris visit is the Navigo Easy Pass. You get one at Metro stations or newsstands bearing a RATP sign. For around $19, the card comes loaded with 10 fares (a "carnet") on the city bus/metro system, which includes free transfers within the Metro. You can buy fewer fares if you wish, but the carnet provides around a 20% savings. You reload the card at machines in the stations or with the IDF Mobilites app. Download and open the app, scan your Navigo Pass with your phone, and you can then top it up in seconds. You can even use your phone in place of the Pass if you prefer.

We've been using the Metro to get to wonderful places on the edges of Paris that relatively few tourists visit, such as Butte aux Cailles, Buttes Chaumont, Parc de Bercy, La Villette, and Bois de Vincennes.