LONDON -: Across Europe, historic cities are buckling. Mass tourism, encouraged by cash-hungry councils after the 2008 crash and fuelled by the explosion of cheap flights and online room rentals, has become a monster. The backlash, however, has begun. In the past decade, the number of low-cost airline seats available each year in Europe has risen by more than 10% annually, more than doubling to more than 500m. Meanwhile Airbnb, the biggest but far from only holiday lettings platform, has reported triple-digit growth in several European cities over the past five years, driving 10 of them to ask the EU for help. The cities have between 10,000 and 60,000 listings each. The net result is that over the course of a year, popular short-break destinations such as Barcelona and Amsterdam are hosting 20 or more visitors for each inhabitant, prompting angry protests from locals and forcing city halls to take action. It is not always evident, however, what that action should be – or if it will work. The trade-off between the revenues and jobs generated through tourism and quality of life is a tricky one. So the idea is not discouragement but management, say city halls.