In the 1660s and 1670s, Versailles was transformed from the small hunting estate used in the reign of Louis XIII into the most impressive royal residence in Europe. One of the most important parts of the building was the series of rooms (salons) known as the grands appartements du roi, which stretched along the northern edge of the C-shaped palace building. The use of a series of state rooms was a fairly standard design feature of early modern courtly palaces: the series could be used as a means of regulating access to the royal person, so that on occasions of state, such as ambassadorial audiences, visitors would be allowed to move through the rooms sequentially. The grands appartements du roi at Versailles were an adaptation of the series of state rooms that already existed in the Louvre, and were designed to follow more or less the same ceremonial rules. In Versailles, the rooms were to be decorated as part of a scheme designed by Charles Le Brun. Each room in the series was named in honour of a figure from classical mythology, and their ceilings were decorated accordingly: moving westward, the visitor would move though the salons of Venus, Diana, Mars, Mercury, Apollo and War, ending up in the great Hall of Mirrors.