The Basel Problem is a famous question from the 17th century. It asks for the exact value of the infinite sum 1 + 1/4 + 1/9 + 1/16 + 1/25 + … For many years, mathematicians could not find the answer. In 1734, Leonhard Euler solved it and showed that the sum equals π² / 6. This surprising result connected an infinite series with π, a number usually related to circles. Euler’s solution was a major breakthrough and became one of the most beautiful results in mathematics.