The art of Iranian carpet weaving, with its long-standing history, encompasses a variety of weaving regions, historically categorized by their prevalent styles as urban, rural, and nomadic carpets. Iranian carpet is a regional and ethnic art form, and this diversity in weaving regions has led to the formation of a diverse structure of carpet designs and motifs. Each region, carrying its own unique identity and ethnic components, possesses specific elements and motifs that have contributed to structural transformations in carpet weaving. In general, Iranian carpets can be classified into two major groups: nomadic carpets and rural/urban carpets. Urban and rural carpets are typically woven in fixed workshops, and their weaving quality varies from the coarsest to the finest types. Older rural Iranian carpets, much like nomadic weavings, were either woven intuitively (mental weaving) or by using “Ornak” (cartoons/patterns). In the contemporary period, specifically from the 1940s onwards, this method gradually changed due to transformations in rural life and increased connections with major urban centers, leading to the use of patterns and the rise of urban-style carpet weaving in villages.Since carpet weaving is prevalent in various regions of Iran, and each region has its own specific design and motif, Nahavand is considered one of the important regions for rural-style carpet weaving with a distinct indigenous identity. Key characteristics of Nahavand carpets include large dimensions, narrow “do-zar’i” (two-zar) sizes, wide borders, and rarely “zar-o-nim” sizes, often featuring relatively sharp red and blue tones. Among these, the Nahavand region is known for a diverse variety of carpets, including a range of Lachak-Toranj (corner and medallion) designs. Due to their specific characteristics, Nahavand’s Lachak-Toranj carpets are easily distinguishable from similar designs in neighboring areas. The most famous pattern of this city and its surrounding villages is known as “Seh-Gol” (three flowers) or “Seh-Kalleh” (three heads), with the best examples woven in the villages of Oshvand (east of Nahavand) and Zaramin (south of Nahavand).The main issue of the present study is to understand the formal structure of Lachak-Toranj carpets in the Nahavand region in order to document the carpets of this area over the past five decades. Therefore, the goal of this research is to examine the structure of designs and motifs and to recognize the diversity of carpets in the Nahavand region. This study seeks to answer the primary question: How has the Lachak-Toranj design been manifested in Nahavand carpets? It aims to identify and introduce the carpets designed and woven in this region from five decades ago to the present, with a specific focus on the importance of Lachak-Toranj designs. The significance of this topic lies in the need to familiarize ourselves with the motifs and specific designs of this region through documentation. Furthermore, despite the importance of identifying these carpets, no comprehensive research has yet been conducted to classify them. Therefore, this study addresses the formal transformations that have occurred in Nahavand’s Lachak-Toranj carpets over the last five decades and investigates the design, motifs, and diversity in their formal structure. Since this region has not been immune to contemporary changes, carpets with specific regional components have been shaped under the influence of these developments. Data collection was performed using library research, field studies, and the gathering of visual documents. The results of this study indicate that carpets in this region, following a rural style, consist of geometric (“broken”) motifs. Despite their simple patterns, these rural carpets possess a component of diversity. Plant and animal motifs, such as birds, objects, and vases, are also present. In the Nahavand region, various villages—including Borjak, Bansareh, Dehlaq, Zaramin, Kalleh Khan, and Oshvand—feature nineteen distinct designs, utilizing structures such as Lachak-Toranj, Toranj-dar (medallion), Derakhti (tree-pattern), Afshan (scattered), and Mehrabi (prayer niche) arranged sequentially or superimposed. Among these, the Barg-e Bidi (willow leaf), Tofangi (gun), and Taghari (pot) designs have fallen out of use. Consequently, the majority of carpets feature a Lachak-Toranj structure, with the highest number of samples originating from the village of Oshvand. By studying the regional designs, it became clear that Lachak-Toranj carpets have represented indigenous motifs along with naturalistic elements within a geometric formal structure.