This project is the design of museum which has located in Taq-e-Bostan Complex. Taq-e-Bostan is a site with series of large rock reliefs from the era of Sassanid Empire of Persia. I want to design a historical museum. The main concept of this project is that the museum has presented the different period of history since Sassanid Empire until now. By this concept, I design two exterior extensions to the Taq-e-Bostan Mountain for the entrance and exit of the museum. They have to show the present time and the galleries are inside the mountain has to present the past. By entering the museum, visitors feel the present time and by entering the galleries they feel that they are in the past from Sassanid Empire and by exiting museum they are feeling present time again.