A courtyard house is a type of house—often a large house—where the main part of the building is disposed around a central courtyard. Many houses that have courtyards are not courtyard houses of the type covered by this article. For example, large houses often have small courtyards surrounded by service rooms or corridors, but the main rooms are not disposed around a courtyard. Blenheim Palace in England is an example of such a house. The main rooms of a courtyard houses often open onto the courtyard, and the exterior walls may be windowless and/or semi-fortified and/or surrounded by a moat. Courtyard houses of this type occupy an intermediate position between a castle or fortress, where defence is the primary design consideration, and more modern plans in which defence is not a consideration at all. In England the courtyard house was a popular design for large houses in the sixteenth century, after noblemen had stopped building themselves castles, but before thoughts of defence were altogether forgotten in the planning of country houses.