On April 14, after more than 500 days alone underground, a Spanish mountaineer emerged from a 230-feet deep cave with a huge grin.

“How would you feel if you had a dream and you fulfilled it?” 50-year-old Beatriz Flamini said after being asked why she was smiling, per NPR. “Would you come out crying?”

Flamini, who is from Madrid, is an elite athlete who may have just broken the world record for the longest time spent in isolation, reported The Associated Press, but it hasn’t been confirmed yet.

Flamini was part of a project called Timecave that studies the effects of isolation on the human body and mind, reported The Associated Press.

She spent 509 days in isolation and 500 days underground — her team said that she came out of the cave around the 300th day but stayed in a tent alone while they fixed some technical issues with her video gear, reported Reuters. Although she was alone, her team was monitoring her constantly and offered support by removing her waste and leaving food and water at a predesignated drop-off point.

Without sunlight to orient her around time, she said that it felt like it wasn’t passing at all and it always felt like 4 a.m., she explained in a Reuters video. She passed the time by exercising, recording video journals to document her experience, drawing, weaving, painting, knitting and reading. She made it through 1,000 liters of water and 60 books.

There were good and bad moments, the athlete said, but “both have been the ones that made me fulfill the 500 days,” per The Guardian.

When asked how she did it, she said by retaining “coherence,” per Reuters.

“You have to remain conscious of your feelings,” she told the crowd gathered after watching her emerge from the cave, per Reuters. “If you’re afraid, that’s something natural but never let panic in or you get paralyzed.”

She described the experience as “unbeatable,” and told reporters that she “didn’t want to come out,” per The Associated Press.

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