Yes, you can generally leave the airport during a long layover in France, provided you meet the necessary immigration and visa requirements. If you are a citizen of a country that has a visa-waiver agreement with the Schengen Area (such as the U.S., Canada, or the UK), you can simply clear passport control and enter France. However, if your nationality requires a visa for the Schengen Zone, a standard Airport Transit Visa (ATV) will not allow you to leave the international zone; you would instead need a valid Schengen Visitor Visa. For a 2026 layover at Paris-Charles de Gaulle (CDG), you should ensure you have at least 6 to 8 hours of buffer time. While the RER B train can get you into central Paris in about 45 minutes, you must account for time spent clearing immigration, stowing luggage, and the mandatory 2 to 3-hour window needed for security and boarding upon your return to the terminal.