Is a traditional Moroccan house or palace with an interior garden. The word riad comes from the Arabian term for garden, "ryad". The ancient Roman city of Volubilis provides a reference for the beginnings of riad architecture during the rule of the Idrisid Dynasty. The design of these courtyard dwellings in the coastal regions of Morocco were an adaption and modification of the Roman villa. When the Almoravids conquered Spain in the 11th century they sent Muslim, Christian and Jewish artisans from Spain to Morocco to work on monuments. These artisans brought with them the idea of arranging the rooms of the house around the central open-air courtyard that has become today's riads. The riads were inward focused which allowed for family privacy and protection from the weather in Morocco. This inward focus was expressed in the central location of most of the interior gardens and courtyards and the lack of large windows on the exterior clay or mud brick walls. Entrance to these houses is a major transitional experience and encourages reflection because all of the rooms open into the central atrium space. In the central garden of traditional riads there are often four orange or lemon trees and possibly a fountain. The walls of the riads are adorned with tadelakt plaster and zellige tiles. The style of these riads has changed over the years, but the basic form is still used in designs today. Recently there has been a surge in interest in this form of house after a new vogue of renovation in towns such as Marrakech or Essaouira. Many riads are now used as hotels or restaurants.