If you’re planning a trip to Spain or elsewhere in Europe this summer, you may come across more than just beautiful architecture and charming cafes—you might also see signs of growing frustration among locals. In cities across Spain, Portugal, Italy, and beyond, residents have taken to the streets to protest what’s being called “overtourism.” The signs say things like “Tourists go home” and “This isn’t Disneyland.” But what’s behind these protests, and what can you do as a traveler to be part of the solution, not the problem?