A few months ago, Madrid woke up with a question: who is Marina Prieto? That's what thousands of Spaniards asked when they came across the photos of a 100-year-old in Madrid's subway stations. Overnight, Marina's Instagram photos of her watering her plants, eating churros, or taking a nap filled the hundreds of advertising spaces in the capital. People started searching for her, discussing her on social media and even taking selfies with the photos. The question on every Spaniard's mind was: who is this lady, and how had she ended up there?