Every August, two different Basque cities hold a festival called, in Spanish, Semana Grande, and in Basque, Aste Nagusia. Visitors planning a trip around one routinely find dates, history, or ticket information for the other, because most English-language coverage treats the shared name as evidence of a shared festival. It isn’t. San Sebastián’s Semana Grande and Bilbao’s Aste Nagusia are organized by two separate city governments, run on different weeks, and have completely unrelated founding stories separated by more than a century.
The mix-up is not a harmless detail. Someone who assumes both cities are celebrating the same event on the same schedule can show up in the wrong city on the wrong dates, or miss the specific thing each festival is actually known for: San Sebastián’s is built around a judged, internationally competitive fireworks contest with six decades of documented history, while Bilbao’s is a neighborhood-driven festival invented by a 1978 citizen contest. Confusing them means missing what makes each one distinct.
This account draws on San Sebastián’s own tourism board records, Basque regional press coverage of the fireworks competition’s 60th anniversary, and the sourced history maintained on the festival’s Spanish-language Wikipedia entry, cross-checked against its own cited references in El País and El Diario Vasco. Every fact below is confirmed by at least two independent sources.
Two Cities, One Translation, No Relationship
Both names mean the same thing. Semana Grande is Spanish for “Big Week.” Aste Nagusia is the Basque equivalent, and both San Sebastián and Bilbao use the Basque and Spanish names interchangeably in their own official materials. That is the entire source of the confusion: two unrelated municipal festivals happen to translate to the identical phrase.
San Sebastián’s edition runs the week framed around the August 15 Feast of the Assumption. In 2026, it runs Saturday, August 8, through Saturday, August 15. Bilbao’s version begins on the first Saturday after August 15, which in 2026 falls on August 22, running through August 30. The two festivals never overlap, and a full week separates them, which means a visitor working through the Basque Country in August could genuinely attend both, provided they know the dates belong to different cities in the first place.
San Sebastián’s festival is also the older of the two by a wide margin. Its roots trace to 1876, in a city whose Belle Époque character and own layered history go well beyond its festival calendar. Bilbao’s familiar modern format, with its neighborhood clubs and street bars, was not invented until 1978, more than a century later, following a city-run public idea contest. San Sebastián’s Semana Grande does not have an equivalent relaunch story. It grew gradually from its 19th-century start into the festival that exists today, without the sharp before-and-after break that defines Bilbao’s history.
What Actually Started in 1876
San Sebastián’s Semana Grande began in 1876, the same year the city emerged from the Third Carlist War, which had left it under siege and bombardment from the surrounding hills. The city’s civic and business community pushed to revive San Sebastián’s tourist economy in the years that followed, and by 1879 the summer program had picked up the marketing name that stuck: Semana Grande, printed on posters that spread the name across the Basque Country, Aragón, La Rioja, Navarra, and the neighboring provinces of southern France.
San Sebastián’s city council gradually took over organizing the week itself, layering in music, dances, and fireworks displays as the festival’s scope expanded. What had started as a single summer promotion grew, year over year, into the multi-day civic festival recognized today, without any single dramatic refounding moment. That slow, continuous growth is the opposite of Bilbao’s story, and it is precisely why treating the two festivals as interchangeable versions of the same tradition gets the history backwards in both directions.
The Fireworks Competition Is Not Just a Display. It Is a Judged Contest.
Most coverage describes San Sebastián’s fireworks as a nightly show. It is more specific than that: it is a formal, judged international competition, the Concurso Internacional de Fuegos Artificiales, founded in 1964 by San Sebastián’s Center for Attraction and Tourism, whose board of local merchants modeled the idea on the success of the city’s own film festival in building a signature summer draw.
A different pyrotechnics company competes each night of the festival, launching its display from the Alderdi Eder gardens beside San Sebastián’s city hall, out over La Concha bay, framed by Mount Urgull, Mount Igüeldo, and Santa Clara island. An official jury scores each display on musical synchronization, color palette, creativity, and overall impact, and awards three tiers of prize: the Concha de Oro (Golden Shell), Concha de Plata (Silver Shell), and Concha de Bronce (Bronze Shell). Pirotecnia Zaragozana won the very first Concha de Oro on August 11, 1964, and returned to compete in each of the competition’s first eight editions.
The 2026 edition, running nightly at 22:45 from August 8 through 15, marks the competition’s 60th anniversary. Over six decades it has drawn pyrotechnics companies from Spain, Italy, Portugal, France, Germany, the United Kingdom, Japan, China, Brazil, the United States, and roughly a dozen other countries. San Sebastián’s own tourism board recommends watching from the La Concha promenade, Paseo Nuevo, Mount Urgull, Mount Igüeldo, the old town’s terraces, or from boats anchored in the bay itself. It is free and open to the public every night of the festival.
The Program Most Visitors Never See Beyond the Fireworks
The fireworks are the best-known draw, but Semana Grande runs a full parallel civic program that generic guides tend to skip entirely. The festival opens each year with the cañonazo, a cannon shot fired from the Alderdi Eder gardens at 19:00 on the opening Saturday, followed by a performance of the traditional “Artillero” song, a distinct ritual from Bilbao’s rocket-and-herald opening at the Teatro Arriaga.
On the sporting side, the Copa de Oro, San Sebastián’s marquee flat horse race, runs at the Hipódromo de San Sebastián in Zubieta, drawing top horses from Spain and France as one of the highlights of the festival’s closing days. Herri kirolak, exhibitions of traditional Basque rural sports, a beach volleyball tournament, and an open-water swim crossing from nearby Getaria round out the athletic calendar.
Family and street programming includes its own gigantes y cabezudos processions, entirely separate from Pamplona’s comparsa, plus workshops, a nightly disco, and a toro de fuego display: a wire-framed, firework-loaded rig carried by a performer who chases onlookers through the crowd after dark. It is a pyrotechnic device, not a live animal, and functions purely as festive street theater. Daytime and evening concerts, txistu and txaranga street bands, and neighborhood txosnas run throughout the week, organized jointly by the city council and Donostia Kultura, and the festival closes on August 14 with the Salve, a religious ceremony held at the Basílica de Santa María del Coro in the old town.
Frequently Asked Questions
What is Semana Grande in San Sebastián?
Semana Grande, known in Basque as Aste Nagusia, is San Sebastián’s main summer festival, held the week framed around August 15 each year. It centers on a judged international fireworks competition over La Concha bay, alongside horse racing, gigantes y cabezudos parades, concerts, and street festivities dating back to 1876.
Is San Sebastián’s Semana Grande the same as Bilbao’s Aste Nagusia?
No. They are two separately organized festivals in two different Basque cities that happen to share a translated name. San Sebastián’s dates to 1876 and centers on its fireworks competition; Bilbao’s dates only to a 1978 citizen-led relaunch and centers on neighborhood clubs called konpartsak. In 2026 they run on entirely separate weeks, San Sebastián’s from August 8 to 15 and Bilbao’s from August 22 to 30.
When is Semana Grande in San Sebastián 2026?
San Sebastián’s Semana Grande 2026 runs from Saturday, August 8, through Saturday, August 15, opening with the traditional cañonazo cannon shot at 19:00 from the Alderdi Eder gardens.
How old is San Sebastián’s fireworks competition?
The Concurso Internacional de Fuegos Artificiales was founded in 1964 and reaches its 60th edition in 2026, making it one of the oldest and most established fireworks competitions on the international calendar.
Every article on the Encierro blog is authored or reviewed by active bull runners with direct experience in Pamplona.