There is a ritual that is repeated on Sundays at an imprecise hour between noon and lunch. It takes place all over Spain with subtleties and peculiarities. As the churches empty, the bars fill up with a different kind of parishioner, but one with equal devotion. It’s the time for vermouth, an important ritual in Bilbao.

Vermouth comes from the German word wermut, which means wormwood. This is one of the ingredients that is added to wine, along with the herb burning bush, clove, cinnamon and flowers. All these aromas give the vermouth that sweet touch. It’s always been drunk in Europe, but it was in the 18th century that it became fashionable in northern Italy. And from there it was hugely popular in northern Spain. Vermouth was a popular drink in the bars of Bilbao, affordable and refreshing, a ‘must’ on Sundays in the Basque Country.

Making a bad wine aromatic with the addition of a bunch of herbs was a good way of providing this kind of drink for a less wealthy public. That’s why vermouth has always been the people’s drink. But around the middle of the 20th century, to differentiate themselves from the lower classes but without giving up vermouth, many people began to use it in different mixed drinks. This made them closer to James Bond (who enjoyed his martinis “shaken not stirred”) than to the town drunk. The first Spanish references to vermouth as the basis for a cocktail came from the famed Madrid bartender Chicote in a book in 1924. He was following a trend that came from bars in the United States.

Among all the combinations that sprang up in that period, one of the most popular was the mariano. And it still is. Some people say the name comes from the blend of the two most popular brands of vermouth (Martini and Cinzano); others claim that there really was somebody named Mariano who patented the recipe. In any case, its composition is of greater interest than its etymology.

The mariano –some friends affectionately call it the marianito– is a mix of vermouth, angostura and Campari. This drink is a real institution in Bilbao, where it’s also known as a vermú preparado. To combat its alcoholic effects, it can be enjoyed along with some of the special tapas of each different bar. While anytime is a good time to have a mariano (well, maybe you should wait for a respectable hour), midday is when most Bilbaínos take to the streets and the bars and enjoy this drink. If you want to imitate them, take note of the following addresses:

Estoril (Plaza Campuzano 3, Bilbao). “Of the 40 people who may be in El Estoril on a Saturday or Sunday morning, close to 38 are drinking marianitos,” say the owners of this emblematic Bilbao establishment. It’s easy to check that out –and advisable to become number 39.

Ander Etxea (Barrenkale 10, Bilbao). Here the marianos come in colours. Red is the traditional one, while blue uses Curazo instead of Campari. It’s served in a cocktail glass to reinforce that idea of glamour. It’s advised not to have more than two, because ending up on the floor is not glamorous and certainly not James Bond.

Urdiña (Plaza Nueva 5, Bilbao). Here they serve it almost with crushed ice. The ingredients are no secret, but the quantities are. It’s made with Campari, angostura, Tanqueray and Carpano (an Italian vermouth). They never add an olive because it kills the flavour, but they do add a few drops of orange juice, which is more tasty than the skin.

El Ayala (Manuel Allende 18, Bilbao). This bar is famous for two things: its octopus tails and its marianito. They insist that part of the secret is to oxygenate it a good deal, so watching them prepare it is a real experience.

Laterío (Aretxaga 3, Bilbao). Here they dare throw in more local products with an Italian touch. You’ll go for the marianitos, but you’ll stay for the Txakoli Spritz.