Kirman is an old and historic city, which embraces several of prominent monuments, especially in the south-east region of Iran. One of them is a domed building that is known locally as, ” Gunbad-i Jabaliyeh or Jabal-i Sang” , located to the east of Kirman City, adjacent to Sahib Zaman mountain. Owing to octagonal form and its stone material of construction, which is rare in this area, it drew attention of any curious scholar and visitor. These varieties alongside with its specific ratio, has made it an attractive and partially mysterious building; also, its background and function are mainly unknown to the public. Hitherto, many papers have been published on history and architecture of this monument, however through re-examining its architecttural features, this study tried to firstly explain its main characteristics, and to shed light on its original function. Secondly, reviewing all facts and materials, suggest a new date for its construction. Thirdly, owing to the structural feature of the building such as, thick walls, the ratio of the inner diameter of building to the height of it and the form of construction, gauge the original dome of the building as a double shell one. In addition, this study aims to assess and reevaluate its role and impacts on formatting the octagonal monuments, as a new type in the funeral architecture of Iran. This study has been carried out by a descriptive – analytic method, field work and applying a comparative study. The findings of the research show that firstly, the monument was built as a commemorative structure with funerary function. Secondly, the date of its construction probably goes back to the late years of the 4/10 century. Thirdly, the octagonal form of the building and its exterior features has been an inspiration for constructing other octagonal and polygonal mausoleums in the architectural history of Iran.