A riad (Arabic: رياض) is a traditional Moroccan house or palace with an interior garden or courtyard. 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. An important design concern was Islamic notions of privacy for women inside residential gardens. When the Almoravids conquered Spain in the 11th century they sent Muslim, Christian and Jewish artisans from Spain to Morocco to work on monuments.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. This design principle found support in Islamic notions of privacy, and hijab for women. 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, usually with Arabic calligraphy, with quotes from the Quran.