This inward focus was expressed with a centrally placed interior garden or courtyard, and the lack of large windows on the exterior walls, which were built of rammed earth or mud brick. This design principle also found support in the social mores of Islamic society, which placed great value on privacy and encouraged a separation between private family spaces (where women notably lived and worked) and semi-public spaces where outside guests were received.[6][59] The walls of traditional houses, if the owners had enough means, could also be adorned with characteristic stucco decoration and zellij tiles, and sometimes with Arabic calligraphy.[60][61] Many richly-decorated mansions built by wealthy or bourgeois Moroccan families have survived in various states of preservation.