Excavations of Jerash, known as Gerasa in Classical times, began in the 1920s, bringing to light one of the best preserved and most original Roman cities in the Middle East. It was during the Hellenistic period of the 3rd century BC that Jerash became an urban centre and a member of the loose federation of Greek cities known as the Decapolis. From the 1st century BC Jerash drew considerable prestige from the semi-independent status it was given within the Roman province of Syria. It prospered greatly from its position on the incense and spice trade route from the Arabian Peninsula to Syria and the Mediterranean. Jerash lost its autonomy under Trajan, but his annexation of the Nabataean capital Petra in AD 106 brought the city even more wealth. By AD 130 ancient Gerasa was at its zenith. Having become a favourite city of Hadrian, it flourished both economically and socially. After a period of decline in the 3rd century, it enjoyed a renaissance as a Christian city under the Byzantines, notably in the reign of Justinian (AD 527–65). The Muslims took over the city in 635, and it was badly damaged by a series of earthquakes in the 8th century. The final blow to the city was dealt by Baldwin II of Jerusalem in 1112 during the Crusades.

The city is reached through Hadrian’s Arch , built in honour of the Roman emperor. Alongside is the Hippodrome , where Gerasa’s chariot races and other sporting events took place, and a little way down the track is the South Gate , part of the 4th-century AD city wall. To its left, and on a prominent rise is first the Temple of Zeus , and then the South Theatre , which nowadays is used as a venue for the Jerash Festival. The most unusual feature of the Roman city is the Oval Plaza  (1st century AD) which, with its asymmetrical shape, is a unique monument from the Roman world. The plaza, 80 m by 90 m (262 ft by 295 ft), is enclosed by 160 Ionic columns. Beneath its stone paving runs a complex drainage system. From here, going north, is the Cardo , a spectacular paved street about 600 m (660 yards) long, which was lined with the city’s major buildings, shops and residences. Chariot tracks are visible in the stones. To the left lies the Agora , the city’s main food market, which had a central fountain. At the Tetrapylon (crossroads) the Cardo meets a second major street, the South Decumanus , which runs east–west. Further along on the left side of the Cardo is the 2nd-century Nymphaeum , a lavish public fountain. One of its basins has a design of four fish kissing. Nearby is the impressive Temple of Artemis , the patron goddess of the city in Greek and Roman times.

Close to the Temple are the remains of several Byzantine churches. The largest is usually referred to as the Cathedral . There is also a complex of three churches, dedicated to SS Cosmas and Damian, St John the Baptist  and St George , which dates back to AD 526–33 and has fine mosaic floors. Further along the Cardo, to the right, is the Propylaeum Church  with the remains of an ornate plaza in front, while next to it are the ruins of an Omayyad Mosque . Beyond lie the unexcavated West Baths , which preserve a splendid domed ceiling. At the North Tetrapylon , once marked by a dome resting on four arches, the road to the left leads to the small North Theatre .

Allow at least half a day to see the ruins, and finish off with the Museum , displaying sarcophagi, statuary and coins.