Tourists have become more than just a nuisance in cities like Barcelona, where anti-tourism marches have taken place. And it's not only the sheer number of visitors that has become a strain - we hear from the charity Venice in Peril, which conserves works of art and architecture, about the physical damage caused by repeated overflows of seasonal tourists. We hear from holiday hotspot Amsterdam, which is also seeking to curb the influx of people - the city receives 17 times as many tourists each year as it has residents. And travel expert Simon Calder leads us through the role of cruise ships, which account for much of the growth in tourist numbers globally. We hear about the impact this has on the Orkney islands, off the coast of Scotland. (Picture: Disney Magic cruise ship returning to dock in Venice; Credit: David Roark/Disney via Getty Images)