The vaulted passageway under the courtyard of the Temple of Zeus is a good starting point in Jerash's ancient city. When your eyes become accustomed to the gloom, you’ll see a superb display of columns, pediments and masonry carved with grapes, pomegranates and acanthus leaves. This is the place to brush up on the three main column styles: Doric, Ionic and Corinthian.
Take a look at the model of the Temple of Zeus, as it will help to recreate the ruins in your mind later.