title: Mona Lisa
context: Leonardo da Vinci is thought by some to have begun painting the Mona Lisa in 1503 or 1504 in Florence, Italy.[27] Although the Louvre states that it was "doubtless painted between 1503 and 1506",[10] the art historian Martin Kemp says there are some difficulties in confirming the actual dates with certainty.[17] In addition, many Leonardo experts, such as Carlo Pedretti [4] and Alessandro Vezzosi,[5] are of the opinion that the painting is characteristic of Leonardo's style in the final years of his life, post-1513. Other academics argue that, given the historical documentation, Leonardo would have painted the work from 1513.[7] According to Leonardo's contemporary, Giorgio Vasari, "after he had lingered over it four years, [he] left it unfinished".[12] Leonardo, later in his life, is said to have regretted "never having completed a single work".[28]
question: When was the Mona Lisa painted?
answers: between 1503 and 1506