Venice is planning to divert massive cruise liners. Barcelona has cracked down on apartment rentals.
Both are at the forefront of efforts to get a grip on "overtourism," a phenomenon that is disrupting communities, imperiling cherished buildings and harming the experience of travelers and local residents alike.
Tourism-phobia has become increasingly prevalent, particularly in European destinations where visitors crowd the same places at the same time.
The backlash has even given rise to slogans such as "Tourists go home" and "Tourists are terrorists."
"This is a wake-up call," Taleb Rifai, secretary general of the United Nations' World Tourism Organization, told tourism ministers and industry executives last week at the World Travel Market in London.
The resentment could rise as tourism increases. The UNWTO forecasts 1.8 billion trips by 2030, up from 1.2 billion in 2016. Add in the 5 billion domestic trips now, and that's a lot of tourists. Cheap airfare is helping to fuel the growth, along with massive growth in international travel from countries like China.
Yet many destinations rely on tourism as a primary source of jobs and prosperity. Tourism accounts for around 10 percent of the world's annual GDP, bringing hard currency into many countries that desperately need it, like Greece.
But tourism can also harm the quality of life for residents, with packed beaches, locals priced out of housing and congested streets in the narrow byways of European cities dating back to medieval times. Longer term problems include environmental damage and the long-term sustainability of cities as viable places to live and work.
For all these reasons, managing tourism is a prominent topic of debate in the industry and a central theme at the World Travel Market.
Rifai, who leaves the UNWTO at the end of the year, dismissed the idea that growth is "the enemy." Pulling up the drawbridge, he argued, would be irresponsible when tourism accounts for one in 10 jobs worldwide.
What is required, he stressed, is the need to manage tourism in a "sustainable and responsible" way that benefits local communities.
Efforts to manage overtourism are becoming more innovative and increasingly tapping new technologies. For example, apps can help tourists visit popular destinations at less busy times. And while critics say Airbnb has priced out locals, its supporters say home rentals can ease pressure on cities by spreading visitors far and wide.
Patrick Robinson, Airbnb's director of public policy for Europe, Middle East and Africa, noted that last year 69 percent of the platform's users in Amsterdam stayed away from the city center.
In some cases, tourist quotas make sense. In the Galapagos Islands, Ecuador has imposed a 100,000 annual limit on visitors. The Croatian city of Dubrovnik, where visitor numbers surged after the Adriatic Sea resort was used as a setting for the series "Game of Thrones," has mulled limiting those entering the city's medieval walls to 4,000 daily.
Other strategies include promoting offseason visits, opening up new destinations or tweaking marketing. Prague is pushing local walks off the beaten track, while London promotes neighborhoods such as Greenwich and Richmond.
"There is no one solution for all, every destination is different," said Gloria Guevara, the new president and CEO of the London-based World Travel & Tourism Council.
Barcelona, which became a tourist juggernaut after the 1992 Olympics, has outlined measures to balance the needs of locals and visitors. The city has cracked down on unlicensed rentals and established a tourism council that includes residents, business, unions and government. The hope is that by listening to all the stakeholders, Barcelona can reduce the strains tourism places on the city and ameliorate tensions between residents and visitors.
"Businesses do not want to put their customers in places where they are being treated as an unwelcome pest, and I think some of the language that we've seen that's hostile to tourism verges on hate speech," said Tim Fairhurst, head of strategy and policy at the European Tourism Association.
Venice has witnessed a tourism backlash in response to the monumental increase in visitors, many of whom irk locals by going to the same spots at the same time.
"The problem at the moment is the intolerable concentration of human numbers in these small spaces which are still thoroughfares in what is still a living city," said Jonathan Keates, chairman of the Venice In Peril Fund.
Last week, a plan was announced to block giant cruise ships from steaming past Venice's iconic St. Mark's Square. Few think it's enough, and there's talk of higher taxes on tourists, timed tickets to venues or even the introduction of turnstiles.
Everyone, though, has a role to play, including the tourists themselves.
Venice recently introduced the "Enjoy Respect Venice" initiative which controls, fines or disciplines travelers who strip and jump into the canals or who eat on church steps. The new measures, according to Keates, clamp down on those "treating the place as a kind of extended marble beach rather than a viable city."
Fairhurst said "simple measures" can make a difference, such as changing opening hours or increasing parking facilities.
"There are lots of ways in which we use our cities inefficiently, where with a much more holistic and long-term approach, we could do better," he said.
Associated Press writer Barry Hatton contributed to this story.