A Visual Representation of the Physical Changes of the Si-o-Se-Pol Bridge Based on Historical and Visual Document Analysis, with a Focus on Toll Gate Modeling

| The historical bridges of Isfahan are among the most valuable historical monuments of Iran, which have been preserved throughout the ages. The unknown original form and future building changes have made it challenging to conserve this valuable heritage. Si-o-Se-pol bridge, which is part of the tangible cultural heritage of the Safavid era, has historical and architectural values. Despite its great popularity, more research needs to be done on it. Few scientific studies have been done on this bridge. Therefore, more research on this building is necessary. Thus, this research deals with the historical and visual documents left by the building and the changes in appearance and landscape of thirty-three bridges over time. This study aims to document the physical changes in the Si-o-Se-pol bridge and its landscape based on available historical and visual documents and the entrance landscape, especially after the construction of the tollgate. This research used a field and archival study. The reading of ancient documents was done along with comparative analyses. A comparison was based on various visual and historical documents, and buildings of similar forms; it led to the presentation of three 3D models. Physical changes in the entrance's landscape and the form of the bridge were exactly modeled. Documenting and modeling the bridge over the ages shows that many changes have been made in the form and landscape of the bridge. The crown on the eastern facade and the toll gate in the northern landscape of the bridge were added to the building in the Qajar period and destroyed in the Pahlavi era. The construction of the toll gate at the northern entrance of the bridge has changed the threshold landscape in this part of the city. Comparative studies and three-dimensional modeling of the bridge in each period proposed three alternatives for the physical form of the toll gate. Archaeological excavations and the possibility of finding other old documents on this bridge can reveal the final alternative in more detail.