With the tourism explosion affecting even smaller cities such as Porto, visitors and locals alike are looking for more ‘authentic’ days out. But is that possible?

“From this point on, we’re going to be trespassing,” announces Margarida Castro casually. “Everyone comfortable with that, right?”

Our group of eight follow her across the threshold of an abandoned house in central Porto, Portugal’s second city. This once-sleepy, cobble-paved place is turning into one of Europe’s hottest tourist destinations, thanks in no small part to sweetener deals with low-cost airlines and a sophisticated government marketing drive.

But being the darling of the 48-hour city break comes with its costs. Old cafes are starting to make way for Starbucks and Costa. Locals are finding themselves outpriced by the boom in short-term rentals. And, while Porto has yet to see anti-tourist protests as in Venice or Barcelona, there’s a growing sense of disquiet.

Facebook Twitter Pinterest Margarida Castro gives a tour in central Porto. Photograph: Miguel Riopa/AFP/Getty Images

And if locals are souring on tourism, so are some tourists. Porto’s sightseeing hotspots can be covered in a day or two, and middle-class city-breakers are looking for something different. A 2016 study by the online travel firm Expedia, for example, found millennial travellers are especially anxious for experiences that involve “living like a local” and finding “hidden gems” off the beaten track.

That suits Castro just fine. A 36-year-old Porto native, she is one of a trio of architects who set up The Worst Tours five years ago. They show people around the city’s disused factories, old railway lines, empty lots and down-at-heel backstreets. The highlight? A downtown shopping mall that went bust in the mid-1990s, now offering cheap rent to cafe bars and practice studios for local bands.

Their “anti-tour” was a response to how tourism was changing Porto. “We were needing to vent and find a way of pouring out our energy and frustrations, so we set up a walking tour to spark political debate,” she says, adding with a smile: “It was either this or hard drugs.”

The Worst Tours is one of string of alternative city tours now popping up in popular tourist destinations around the world. In one way or another, all pledge to pierce the marketing blurb, unveil the real side of their cities and provide an “authentic” experience.

“It’s obvious, no?” says Castro when asked why the format appeals. “No one likes being a tourist.”

Martin Finlayson, a British first-time visitor to Porto who took the tour, agrees. “There are so many tourist bars and restaurants here nowadays,” he says. “I wanted to see what the real Porto was like – you know, where local people hang out, where they eat and drink.”

Facebook Twitter Pinterest Eugene Quinn gives his Vienna Ugly tour. Photograph: dpa picture alliance/Alamy

Locals, too, are looking for novel ways to engage with their home cities. Eugene Quinn leads “urban adventures” around his adopted city of Vienna, including the Ugly Vienna Tour, the Corruption Tour, the Midnight Tour, and even a Smells Like Vienna Spirit Tour, which explores the olfactory delights of the Austrian capital. He says they attract as many as 80% locals.

“It’s a shame that more people don’t actually see their own cities,” says Quinn, who, rather than carrying a flag, wears the orange trousers of the municipal street sweepers.

Castro agrees, arguing that tours aren’t just for tourists, but encourage creativity along the peripatetic tradition of ancient Greece, sparking an exchange of ideas and experiences of urban living. The visit to the abandoned house in Porto, for instance, prompted a discussion about squatting: a common but little discussed practice in the city. Other topics addressed during the four-hour walk included social housing policies, rent hikes, green space and fachadismo – the practice of property developers ripping out the interiors of historic buildings while keeping the facades intact.

Facebook Twitter Pinterest Margarida Castro says that walking through her city and debating with tourists from other cities “keeps [her] ideas in check” Photograph: Miguel Riopa/AFP/Getty Images

“With our salaries, we don’t travel much,” Castro says. “So walking the city and debating with someone from Warsaw or Barcelona about this or that keeps my ideas in check.”

Many sociologists and anthropologists have long considered “immersive tourism”, as the travel industry packages it, to be a futile quest: by the simple act of stepping into other people’s worlds, we change them.

“That the arrival of tourists alters the local community has been a theme from the earliest years of tourism research,” says Dean MacCannell, a sociologist at the University of California Davis and the author of The Ethics of Sightseeing. He gives the example of indigenous women in Peru who traditionally put a flower in their hair to signal their readiness for a romantic relationship. Now, however, the act often merely represents an acquiescence to the photo-snapping visitor.

“Today the flower means only that the woman knows herself to be an object of the tourist gaze,” he says. “What the tourist is seeing is life as it is actually lived by the locals under the regime of tourism.

“If a tourist wants authenticity the industry and hosts will provide it in the form of staged authenticity. But usually it is a fake ‘real-life setting’ for the tourists to explore.”

Facebook Twitter Pinterest A Quechua woman and child have their photographs taken by a tourist for money in Cusco, Peru. Photograph: Dan Kitwood/Getty Images

The Jane’s Walk movement makes a virtue of the limits of genuine immersion: it treats the city tour as a co-creative experience in which participants learn from one another rather than just gawp. Inspired by the urban studies guru Jane Jacobs, Jane’s Walks are pitched as an opportunity for people to “observe, reflect, share, question and re-imagine” the places where they live and work.

How Jane Jacobs changed the way we look at cities | Saskia Sassen Read more

Alia Scanlon, the movement’s Toronto-based coordinator, took a walking group to the city’s main railway station soon after the Yonge Street van attack last April. Protective bollards had been installed at the station’s entrances. “We stood and touched the barriers and discussed how our sense of safety had been affected and whether they made us feel more safe or not,” she says.

In Leeds, meanwhile, the urban consultant and psychogeographer Anzir Boodoo uses the Jane’s Walk model to kick off novel conversations about urban living with his fellow residents. Boodoo has led walks to a former zoo, to a deconsecrated cemetery now buried under a new university campus, and to the city’s bus terminal, timed to coincide with the feast of Terminus, Roman god of boundary stones.

He considers the experiential aspect of anti-tours to be essential. “It’s all about overturning our normal perceptions and interactions with urban spaces,” he says. “With these walks, you can never really know where they’re going to take you.”

Follow Guardian Cities on Twitter, Facebook and Instagram to join the discussion, explore our archive or sign up to receive our weekly newsletter