A doctor who examined the baby, a girl, said she was only one or two hours old. She had a slight cold and was taken to hospital, where she is now said to be in a stable condition.
She was found by two 15-year-old girls in a stairway leading to a cellar in a property in Kaiserstrasse.
The baby was wrapped in a brown jacket and was wearing a grey t-shirt.
Anyone with information that could lead to the baby's mother should call 31 310 43 800.