In 1606 Prince Archbishop Wolf Dietrich von Raitenau had a palace built outside the town walls for Salome Alt which he called "Altenau". Salome Alt was the daughter of the prominent merchant and councillor, Wilhelm Alt, and the prince archbishop's mistress. She bore him 15 children, of which 10 survived. Salome Alt had no political significance.
Today the Marble Hall, formerly the prince archbishop's banquet hall where Mozart's father Leopold and his children Wolfgang and Nannerl once played their instruments, is acknowledged to be one of the "most beautiful wedding halls in the world". The Marble Hall also serves as an elegant venue for conferences, awards ceremonies and exquisite concerts (Salzburg Palace Concerts).
Links: www2.salzburg.info, en.wikipedia.org