If you’re planning on heading out on the town on New Year’s Eve, the RATP has a little gift for you:  free rides on the subway, buses, trams, and RER trains throughout Ile de France from 5:00 pm on December 31st through noon on New Year’s Day. But be advised that the Metro itself only functions in its entirety until 2:15 am. After that, a limited number of lines (and stations on those lines)will stay open. Night bus service will be in effect with certain closures. To get all the details, download the guide.