This article analyzes the architectural designs and ornaments of a 12th century structure in Iran. Friday Mosque of Forumad, Masjid-i Jami' Forumad is a prototype mosque in Persian architecture using an application of ornaments. Architectural ornaments are important examples of practical geometry. The brilliant stucco ornaments, elaborate strapwork patterns with turquoise and cobalt blue, and floral motifs with underlying geometric patterns, made this mosque a worthwhile building in early Iranian-Islamic period. By introducing the mosque's features, the ornaments that adorn some of the walls will be analyzed and geometric methods for constructing their underlying designs will be presented.