The Piano Nobile is the principal floor of a large house, usually built in one of the styles of classical renaissance architecture. This floor contains the principal reception and bedrooms of the house.
The piano nobile is often the second floor above a service floor in the rustic style. The reasons for this were so the rooms would have finer views, and more practically to avoid damp. This is especially true in Venice where the piano nobile of the many palazzo is especially obvious from the exterior by virtue of its larger windows and balconies and open loggias. Examples of this are Ca' Foscari, Ca' d'Oro and Palazzo Barbarigo.
Larger windows than those on other floors are usually the most obvious feature of the piano nobile. Often in England and Italy the piano nobile is reached by an ornate outer staircase, which negated the need for the inhabitants of this floor to enter the house by the servant'Kedleston_Hall" title ="Kedleston Hall">Kedleston Hall is an example of this in England, as is Villa Capra in Italy.
Most houses contained a secondary floor above the piano nobile which contained more intimate withdrawing and bedrooms for private use by the family of the house when no honoured guest were present. Above this floor would often be an attic floor containing staff bedrooms.
This arrangement of floors continued throughout Europe for as long as large houses continued to be built in the classical styles. This arrangement was designed at Buckingham Palace as recently as the mid 19th century. Holkham Hall, Blenheim Palace, Castle Howard are all 18th century English houses which employed this design.