Why is there a walled window in Palazzo Mattei? According to legend, Duke Mattei lost almost all of his possessions to gambling and his future father-in-law was opposed to the marriage of the Duke with his beautiful and rich daughter. Mattei, to prove him he was still a powerful person, ordered that a fountain was built, Fontana delle Tartarughe, in just one night and in front of the windows of the palace. When the future father-in-law saw the majestic fountain changed idea and consented to his daughter's marriage. After that day, the window is walled to prevent other people from looking down.