Construction workers clamp scaffolding onto the historic facade of Colmado Quilez, an old-fashioned general store selling wine and cheese in downtown Barcelona.

One hundred years ago, customers rolled up here in horse-drawn carts. Now BMWs park on the Rambla de Catalunya, which has become one of Barcelona's poshest avenues.

So posh, in fact, that this family business can no longer afford to stay.

"We just can't compete with big multinational chain stores," says manager Faustino Muñoz, who wears a pale blue pinstriped smock at work. "We're struggling to do right by our 14 employees — some of whom have worked here 40 years. But our rent tripled this year."

That's because rent controls, in place for decades, expired this winter in Barcelona and other Spanish cities. So Colmado Quilez is moving into the only space it can now afford — a storage room next door. And its historic storefront is being renovated to host a chain clothing store.

Such gentrification is common in big cities. But Barcelona's has been fueled by a huge spike in tourism. This city of 2 million now gets more than 7.5 million tourists a year. They boost the economy, but put off some locals.

Residents of the beach-side Barceloneta neighborhood have been staging protests. They're angry about Airbnb rentals that host bachelor parties where foreigners rage and vomit in their cobblestone streets all night.

Barcelona's new left-wing mayor, Ada Colau, has said she fears her city could become the next Venice, Italy, "sacrificing itself on the altar of mass tourism."

Colau has said she'll consider limiting hotel permits and cruise ship visits.

But another group of foreigners is actually trying to preserve some of the city's oldest businesses — its mom-and-pop tapas bars.

"We have a market, a great place to have seafood — places you won't find in a guidebook," says Renée Christensen, an American expat and tour guide for Devour Barcelona, a food tour with a social mission. "A lot of these places, too, are places with history. We hope that none of these places will ever close."

Places like Can Tosca, a wood-paneled bar covered with black and white photos of generations of the Tosca family. Rosa Sanchez Tosca, who was born in the stairwell next door, now runs the bar with her siblings.

"Without rent controls, so many emblematic places are closing, and everything is starting to look the same," Rosa says. "We've had two tough years. It's been difficult to meet our expenses. That's why this tour has been crucial for us."

Rosa says the food tour has helped her stay in business. Now, alongside elderly locals at the bar, American tourists bite into Rosa's special botifarra sausage sandwiches.

"We'd never find this place on our own!" exclaims Narissa Nuqui, a tourist from Orange County, California.

"Mmm, delicious! It's a good thing I'm hungry," says Nuqui's husband, J.J.

Christensen leads the tour group through a square where gypsies strum guitars, and into a local olive oil shop, a vermouth bodega, a bakery founded by a Syrian immigrant — and then into the Mercat de L'Abaceria Central, a local market far off the beaten path.

"This market was inaugurated in 1892. That makes it about 20 years older than La Boqueria — that very big, colorful market on Las Ramblas," Christensen says. "Boqueria has kind of become part market, part tourist attraction. It's a shame, but it is a little bit crazy if you go and visit."

La Boquería recently announced new rules limiting large tour groups during certain hours. Vendors have complained about tourists crowding narrow passageways and blocking local shoppers from entering.

"There are millions of tourists who go in and take photos and not buy anything," says U.S. tourist Connie Chung, visiting from San Francisco. "I think a lot of merchants have been devastated because of that."

In contrast, the Albaceria market is deserted except for a few little old ladies buying fish. Here tourists swallow skewers of olives and salt cod from Guiseppe the olive vendor, and sample delicacies from Conchita the cheese lady, who's worked here since she was 12. Many of Devour Barcelona's tourists return after the tour to buy more.

The Devour Tours were founded by Lauren Aloise and James Blick, an American and a New Zealander, respectively. The company runs tours in Barcelona and several other Spanish cities. Both Aloise and Blick are married to Spaniards, and feel strongly about helping to preserve the authenticity they've discovered in Spain — which they believe may be under threat by mass tourism.

"People are sad to see how it's changed, and sad to see how almost every single shop — even laundromats or delis — have all become something that's a big brand," Aloise says.

"And there's nothing wrong with chains! But we don't want to have all chains," Blick chimes in. "It does feel like David and Goliath. But David was smarter! You just have to recognize where that strength lies, and harness it."

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