Like many other cities in Europe, Lisbon’s burger trend has been growing strong, with gourmet versions and strange national adaptations overtaking the capital. But the bifana, Portugal’s quintessential hot sandwich, will always trump any trend for locals who want quick nourishment. Composed of a thin pork filet cooked in a sauce made from white wine, garlic, bay leaves, lemon and lard, the bifana is an irreplaceable cultural habit.

Fresh pomegranates await to be squeezed into juice near Istanbul's iconic Grand Bazaar .

Visiting the Jamaica plant and flower market is one of our favorite activities in Mexico City; we love getting lost in its green alleys and never fail to emerge with at least one new plant and a beautiful bouquet of flowers. And of course, we’re always on the lookout for new places to eat. Our favorite barbacoa joint is in this market, but when we want a different experience we head to the huarache alley, where several stalls offer this tasty Mexican specialty.

There used to be a state-owned publishing house in our neighborhood with a cafeteria that served a proletariat menu that included ostri (beef stew), cold slices of beef tongue and cutlets with buckwheat or mashed potatoes. It was a stolovaya, which is the Russian word for “canteen,” but a more accurate translation would be “human fueling station of protein, carbs and vodka.” It was gutted several years ago; its ghosts now haunt the dining room of a designer hotel.

Tucked away in an alley in Istanbul’s Aksaray neighborhood, Şirket Alahdab is a small grocery store overflowing with Syrian staples: pickled baby eggplants, dried leafy greens, cans of clotted cream for desserts. When we enter the store, Istanbul temporarily fades away and Damascus or Aleppo take its place. “All real,” the clerk declares proudly, as he shows off his goods. “Smuggled from Syria.”

As part of CB's "Usta All-Stars" card project, our intrepid researcher Ali Akas went around town interviewing street food vendors about their work, the food they serve and some of their trade secrets. Besides the cards, another result of Ali's work was this map, which plots the relative locations of some of Istanbul's finest vendors.

A proper way to start one's day is with a fresh cup of black tea from the wonderful tea master Bayram in Karaköy's 16th-century Kurşunlu Han building. It's the first stop on our Two Markets, Two Continents walk.

We were sitting at the counter, trying out the goods, when an elderly man who has clearly had a tough life copped a squat at the next bench. Leaning on a crutch, with only one eye and a very dinged-up forehead, he patted our shoulder to offer us a cup and a pitcher of fresh, cool water. We chatted a bit. Telling us he’s a regular and praising the preparation of the veggies at El Comunitario, he flashed his toothless, but endearing, smile, “What do you think of how much people are paid here?” It was a genuinely pleasant immersion into the social whirl of this community kitchen, located in one of the more troubled corners in the heart of Mexico City’s Centro. We began to pour water into our other neighbors’ cups and chatted with the cooks in the kitchen, enjoying some great, incredibly cheap grub.

A wide variety of reasonably priced fresh fish, shellfish, crabs and kalamari for the customers to choose at the Athens Municipal Market, a stop on our Culinary Secrets of Downtown Athens walk.

Geography-challenged foreigners often come to Brazil with a vague, ill-informed hope of finding good Mexican food. In Rio, that only happens at Ipanema’s Azteka. In fact, there are few restaurants we find as compelling in the touristy beachside neighborhood as this one, focusing on Tex-Mex cuisine adapted slightly for Brazilian palates. The breadbox-sized eatery was established by Miguel F. Campos and his Bulgarian wife, Aglika Angelova, a professional piano teacher, after the couple scouted out a new country in which to start a new chapter of their lives together. The two met at an organic pizzeria in Chicago.

Every late morning from the ground floor of a typical Lisbon building, the façade of which displays a tile-painted Madonna, a hunger-inducing scent pervades the street. Dhaka Restaurante is one of many canteens in the Mouraria neighborhood preparing its lunchtime curry. Along Rua Benformoso, among the small shops selling jewelry, trinkets and Chinese-made goods, are several restaurants that have fed the local community from the Indian subcontinent for years. Today, however, they aren’t just cooking for them. Due to a rapid process of urban transformation, mainly thanks to tourism and interested investors, more and more people from Lisbon and further afield are passing through this winding thoroughfare looking for alternative flavors.

In Tbilisi, we have mornings when we wake up wrinkled and dehydrated, and as we lie in bed knuckling the sleep from our eyes, we hear an all too familiar chorus beckoning us to “bite me, slurp me, gobble me down….” That is khinkali singing, and when you hear the melody, your day has been cast. You can forget about work and responsibilities. We used to fritter away our afternoons with a platter of khinkali at Pasanauri, but when it changed owners and attitude and our beloved waitress Irma packed her bags, it was clear an era had passed. A period of pretty good khinkali at pretty good restaurants followed until we asked local filmmaker and fellow gastromaniac Levan Kitia where he goes for khinkali.

Wave after wave of migration from Anatolia has bestowed upon Istanbul a population of 15 million at bare minimum, with countless pockets of the city representing villages and districts from every last corner of the country. In the neighborhood of Feriköy, those originally hailing from the eastern province of Erzincan have managed to consolidate their presence on an entire street. Lined with a number of restaurants and shops selling fresh goods typical of the province, and a row of village associations established for the purpose of maintaining cultural ties between those living in Istanbul and their relatives back home, Feriköy's Gediz Sokak is all about Erzincan, a land of sheep and mountains famed for its dairy products.

After four generations of doing business in the same shop – housed since 1907 in a beautiful moderniste building between Paseo de Gràcia and Gran de Gràcia – the beloved patisserie La Colmena has closed. One of Barcelona’s most iconic and historic establishments, La Colmena made some of the best artisanal candies, turrón de Jijona, Lenten fritters and Swiss rolls (called a brazo de gitano, or “Gypsy arm” in Spanish) in the neighborhood, and was run by siblings Cristina and Francesc Font, the fifth generation of the family. The venue was effectively forced to close because its rent was set to more than triple, and because of a requirement by City Hall that they restore and update the premises. Although Barcelona residents were aware of the situation, the owners’ decision to close still came as something of a shock to longtime customers.

Beneath modern Lisbon lies a complex network of galleries belonging to the city’s 18th-century aqueduct, a monumental structure that resisted the 1755 earthquake that devastated much of the capital. The aqueduct’s 58 km of tunnels and underground channels distributed water to 33 chafarizes (fountains) – often ornamental – to supply the city with drinking water. One of them, located along the steep steps connecting the Avenida and Príncipe Real neighborhoods, now houses Chafariz do Vinho, the Portuguese capital’s oldest enoteca, or wine bar.