The day before the first total solar eclipse on the Spanish mainland in more than a century, Mar Carretero-Castrillo, a 28-year-old astrophysicist, climbed the hill in the tiny and remote northern Spanish village where she spent her childhood summers staring up at the starry night sky.
Ms. Carretero-Castrillo had returned home from her job overseas for the big celestial event, she said, with the “beautiful idea” of gathering a small watch party on the same hill to quietly experience the eclipse with snacks, scientific discussions and educational games played with kitchen colanders.
“But we have this fiesta,” she said, looking down to the normally isolated village of Castrillo de la Reina, which on Wednesday is playing host to “Eclipse-fest,” a party for hundreds of outsiders. The event will be free to the village’s 160 full-time residents as well as the more than three times as many people who spend the summer there. Ms. Carretero-Castrillo wondered if her planned hillside gathering would be overshadowed by the party’s water-gun fight, laser light-show, musicians, and D.J.s playing electronic, punk and reggaeton music until 6:30 a.m. It was possible, she acknowledged, that the fiesta “will interfere,” noting that many people seemed to “prefer partying.”
The largely uninhabited and arid land around the village — known as a setting for the film “The Good, the Bad and the Ugly,” dinosaur fossils and purple-tinted cured beef — is in the path of totality.
As such, it has drawn legions of astronomy enthusiasts from around Spain and the world, looking to experience the eclipse from what would usually be a place of solitude. Yet it has also been pulled into the orbit of the big eclipse-night party, leading Ms. Carretero-Castrillo to worry that a once-in-a-lifetime chance to instill villagers with a love of science was being eclipsed by Eclipse-fest.
“Sometimes, it’s difficult to put a value on science,” she said, wearing a blue T-shirt branded with the logo of the observatory she works for in Chile.
Ms. Carretero-Castrillo was raised in the Canary Islands but spent her summers in the village. Her career as an astrophysicist has since brought her to Barcelona, where she earned a doctorate, and won her acclaim for helping to identify 175 “massive runaway stars,” or stars that move at unusually high speeds across space.
In the days and hours leading up to totality, she did her best to put the emphasis on the heavens, giving presentations and holding eclipse workshops in the area.
She was joined by her family, who wore “Mar’s Stars” T-shirts, and her partner, Martí Roset, 30, a mathematician who killed time by working out number theory equations in his notebook. (“He’s my boyfriend,” she said with a knowing nod to their shared passions.)
On Tuesday morning, she stood between a “Solar Eclipse 2026 in Rural Spain” slide show and a few dozen older residents, many in wheelchairs. This would be the first eclipse on the Spanish mainland since 1905, she said.
“Was anyone here born in 1905?” she said. “Almost?”
Afterward, she sat with them around tables and helped with eclipse-themed crosswords (among the answers: “moon” and “glasses”) and card games in which she helped a 101-year-old woman put the stages of the eclipse in order.
In the back of the room, her father, Juan José Carretero, 60, marveled at his daughter’s commitment to spreading the scientific gospel. Still, his interests were somewhat divided. He’d watch the eclipse up on the hill with her, he said, but he also wanted to check out the party.
“It reminds me a bit of the raves they hold in Spain — raves where people come from various countries,” Mr. Carretero said.
She had originally, she said, hoped to give a scientific talk at the village hall on the day of the eclipse. But the mayor told her “we have many people for the party, I don’t know if we will have the space,” she recalled.
They finally agreed that she could hold it the day before, and it seemed the entire town showed up.
“We have a space problem,” she ebulliently told the standing-room-only crowd. “I’m going to tell you everything you need to know about the eclipse.”
She repeated the presentation she gave the group of older residents, stressing that she was a local girl and encouraging them to join her gathering on Wednesday evening for hilltop colander experiments. At the talk’s conclusion, a 12-year-old boy came up to her and asked what he could do to follow in her footsteps. She told him to keep asking questions.
“The eclipses we had in 1905 really pushed astronomy in Spain,” she said. “This is another opportunity.”
Yet even as she spoke, her competition was already setting up.
During her talk, a black van parked in the square and workers began setting up the D.J. booth and stage. The mayor, Galo Contreras Sanz, sped onto the square, dashed into his office and retrieved eclipse glasses to hand out to the departing townspeople.
Mr. Contreras Sanz said that while only locals came to hear the astronomer’s talk, the party would draw people from all over. (He himself, he said, would watch the eclipse from up in the church bell tower. “The view is going to be amazing,” he said.)
He greeted Ms. Carretero-Castrillo and they spoke politely, but guardedly, about the eclipse and the party. As she left to join her family, friends and dozens of other locals in the town’s watering hole, she and her boyfriend watched tests of the laser lights on the church’s stone tower. The party, her boyfriend said, looked like it was “going to be fun.”
On Wednesday afternoon, as Ms. Carretero-Castrillo gave another packed talk in a nearby town, partygoers started putting up tents and filing into the town hall to collect their orange ribbon wrist bands and Eclipse-Fest hats.
Nacho Donoso, 50, an out-of-towner from Madrid, said the promoter’s parties were always top notch, and for many, “it doesn’t matter that there’s going to be an eclipse.”
But the party’s organizer, Jorge Barrero, who handed out eclipse glasses, picnic-spot recommendations and hats and bracelets, said the eclipse would still be the star of the show.
“The eclipse gives you the right here, the right now,” said Mr. Barrero, 51, a chemist by training and former science ministry employee. He said there would be no music for the minute or so of total eclipse, “out of respect.” The D.J.s would start playing at 10 p.m. and go until a breakfast of churros and chocolate more than eight hours later.
He said he met Ms. Carretero-Castrillo the day before, and invited her to the party. “She told me she’s coming,” he said.
Carlos Barragán contributed reporting.
