They built monuments with increasingly intricate and extensive decoration, particularly in wood and stucco.[1] They were also the first to deploy extensive use of zellij (mosaic tilework in complex geometric patterns).[20] Notably, they were the first to build madrasas, a type of institution which originated in Iran and had spread west.[9] The madrasas of Fes, such as the Bou Inania, al-Attarine, and as-Sahrij madrasas, are considered among the greatest architectural works of this period.[21][22][9] While mosque architecture largely followed the Almohad model, one noted change was the progressive increase in the size of the sahn or courtyard, which was previously a minor element of the floor plan but which eventually, in the subsequent Saadian period, became as large as the main prayer hall, and sometimes larger.[23]