One defining element of the Safavid Dynasty was its ideologically driven religious spirit, which incorporated various beliefs--Christian, Muslim, pre-Islamic Turkish--into devotion to Shiitism. At that time most of Iran was Sunni. The Safavid's Shiitism distinguished the dynasty from its principal rival to the west, the Sunni Ottoman empire. Thus, Shiitism came to be identified strongly with Iran.
Another defining element of the Safavid Dynasty was its literary, philosophical and architectural renaissance. Elements of that architectural renaissance are visible on Isfahan's landscape today. So are elements of the philosophical renaissance: It was as a consequence of the Safavid Dynasty that Persian Shiitism developed its unique brand of clergy-like mullahs, or supreme religious authorities, on one hand, and ruling Shahs on the other.