What amazed me about Bishapur was its size and the fact that it had only been very partially excavated -- there is still much more to learn from it! However, those excavations that have taken place (mostly by the French in the early to mid 20th C, and only in the royal part of town) revealed one of the most astounding things I have seen in an ancient city. Aside from the enormous Palace of Shapur which is impressive, and some excellent mosaics (the best of which are in the Louvre of course), the nearby Anahita's Temple has a stairway leads underground -- what amazing amounts of excavation must have been needed to unearth it -- to a formerly sacred pool, or as some describe it, a fire altar. Because it was so deep, its original masonry is beautifully preserved -- the stones are solid and perfectly shaped together with minimal mortar.
A rectangular shape of the city supposed to be styled for the local climate, the design means that all northern, eastern, and western streets would meet at the center of the city and the rich would live in large gardens. The three main parts of the city were the administration/religious buildings, the amazing Dokhtar castle stretching up the nearby mountain to guard the city and the area outside the wall of the city.
Originally the city was approached along the Shapur River in the steep sided Chogan Gorge, but now the main route comes into the area down the valley, using a different route up the mountains to Shiraz. The paired city of Kazerun, 25km away has also unearthed many beautiful relief work, but few ruins remain. Shapur had an enormous statue of himself carved and placed in a cave about 5km up the nearby gorge, but the hike makes it a bit inaccessible to most visitors.
Nearby on the rock face of the gorge is a series of carvings telling the stories of the Sassanian kings -- what beautiful reliefs! Unfortunately, they have suffered from fundamentalist conservative Muslims in recent years, and many of the heads and carving have been defaced, so security has been tightened.