In the first quarter of the third century CE, the Sasanian dynasty overthrew the Parthian Arsacids, who had until then been ruling an empire that consisted of what is now Iran, Iraq, and parts of Afghanistan. The first Sasanian king, Ardašir, celebrated his victory with a splendid relief near his castle. Soon, a second relief was added, which commemorated his capture of the Parthian Empire, Ctesiphon.
South of these monuments, the conqueror founded a large, circular city, which he called Ardašir Khureh, “fame of Ardašir” (satellite photo; map). His palace is one of the most delightful monuments in Iran, certainly worth a day trip from Shiraz. (Make sure you have good shoes when you decide to climb to the castle.)