Mosques were first built on the Arabian Peninsula. The Muslims who built them used old architectural styles. They also combined these styles in new ways. A major influence was the palaces built during the Parthian and Sassanid dynasties of Persia. The "Sarvestan palace" from the Sassanid era is a good example of this. It has an arched entrance and a central dome. These features already existed in Persia before Islam.