"Why on Earth are you visiting Mulhouse?" the man in the train's window seat asked when he detected my American accent. I explained that I planned to visit two of the best museums anywhere devoted to transportation: Mulhouse's Cite du Train and its Cite de l'Automobile. He shrugged as only the French can and returned to his reading, unimpressed. So I didn't bother elaborating that I planned to see these attractions, and a few others, with my Mulhouse City Pass, which includes, for 18 euros (about $20), free admission to one attraction or museum of your choice, discounts to nine others, and unlimited transit on that Alsatian city's buses and trams.
Two dozen French cities, including Aix, Avignon, Nancy, Metz, Paris and Strasbourg, sell similar passes (us.france.fr/en/holiday-prep/french-city-passes) in 24-, 48- or 72-hour versions that cost between 15 and 74 euros (about $17-$82). The most famous and most expensive of these is the Paris Museum Pass, sold in two-, four- and six-day versions; it allows unlimited visits to the city's museums and monuments (see the Mona Lisa as often as you like) for 48, 62 or 74 euros.
France is not alone in offering tourism passes. There are similar ones for most major cities in the U.S. and Europe, as well as in Asia and Australia. Used judiciously, they all save money compared to buying separate admissions. Even better for people in a hurry, most passes allow you to skip the lines to buy tickets and to gain entry to whatever you've come to see.
Some passes are what I'll call "officially issued," meaning they're created and sponsored by the cities' tourism organizations. In addition, several private companies sell their own branded passes to destinations around the globe, sometimes alongside those sponsored by a local authority.