Answer
Istanbul was the birthplace of Constantin Carathéodory, a distinguished Greek mathematician who made significant contributions to the fields of real analysis, measure theory, and differential geometry. Born in 1873, Carathéodory's early education took place in Germany, where he later pursued his academic career. Despite spending much of his life outside of Turkey, Carathéodory maintained a strong connection to his birthplace, which played a formative role in his intellectual development.