One of the strikingly significant things about the Safavid dynasty--a religious order that over the centuries took on military and political elements--is the many wars that were fought. These wars were at the heart of the great expansion of the empire. It was while the Safavid armies were engaged in the 1533 battle with the Uzbeks that the Ottoman's launched a surprise attack and took Baghdad, holding it thereafter for close to 100 years.
In the long term, they reestablished the importance of the region as a economic power between East and West. This in some ways became part of their downfall as a political power as they appealed to Western powers to side with them in their long-running rivalry with the Ottomans. British presence in the area, especially the East India Company after the early 18th century, helped to drain the empire of the wealth upon which much of its military and political power had been based.
The Safavid dynasty actually ruled the greatest Persian empire since the Muslim conquest of Persia, and one of their key religious contributions was their establishment of the Twelver school of Shi'a Islam as the official empire religion. This was a massive turning point in Muslim history. In addition, let us remember the vast geographical tracts of land that they ruled. the Safavid empire at its height controlled Iran, Azerbaijan, Armenia, Iraq, Georgia, Afghanistan and the Caucasus, as well as significant tracts of Pakistan, Turkenistan and Turkey. In addition, the Safavid empire had the possession of gunpowder, which clearly helped it maintain its power and dominance.
One major aspect of the Safavid Empire is that they were Shi'ite. This helped lead them to come into major conflict with Sunni states such as the Ottomans.
Culturally, this was a time of great artistic development. Things like architectural and building techniques, ways of weaving silk, carpet making and painting all thrived during the Safavid Empire.