El Jem was formerly the Roman town of Thysdrus, one of the most important towns in North Africa after Carthage (now to be found in the suburbs of modern Tunis). The amphitheater was built around the middle of the third century AD and was thought to house up to 35,000 spectators.
Having fallen into some state of disrepair, its blocks being used for building the surrounding town and also contributing to the Great Mosque in Kairouan, the amphitheatre was declared a World Heritage site in 1979. More recently it has been used for filming some of the scenes from the Oscar winning film Gladiator.
It is worth mentioning that the site features one of the cleanest public bathrooms in Tunisia, located about 150 meters to the right of the entrance.
El Jem is more or less equidistant from Sousse and Sfax, lying just off the main road that links those two towns.
By train - A return ticket from Sfax should be around 10 Dinar, and take aprox. 45 minutes. You can just see the top of the collesseum from the train station.
By car - head south from Sousse (north from Sfax) for about 1 hour; the amphitheater is clearly visible as you approach the town and the turn off well signed.
By taxi - one of the most expensive options, this gives you the most flexibility. Either arrange a time for your driver to return or ask him to wait for you. Arrange a price before setting out, and expect to pay 50 Dinar or higher for a return from Sousse or Sfax.
El Jem is a small town and everything that may be of interest to the visitor can be reached on foot.
Train is also a very convenient method. The trains are comfortable and the travel is short. One would be able to take an early morning train from Tunis, see El Jem and take the afternoon train back to Tunis. All in a day and you would have some spare time to tool around in Tunis as well.
The amphitheater dominates the modern town, and was also featured in several scenes of the film Gladiator.
A ticket costs 7 Dinar, and a camera 1 Dinar. The amphitheater closes at 5:30 PM in the Winter, and 7:00 PM in the Summer.
A ticket to the amphitheater also includes entrance to the museum (mini-map on back of ticket). As well as a large selection of mosaics and his has one restored Roman Villa, with all the mosaics in place and gives a real feel for their style of living. Adjoining this is the rest of this area of Roman Thysdrus, with the streets and floor plans laid out over a large area showing the variations to the house and villa plan.
The amphitheater is best seen at dawn or sunset, and this is also the best time for taking photographs. While the grounds may be closed during sunrise or sunset, photographs of the site from the surrounding streets are certainly possible.
Climb to the higher levels of the amphitheater and soak in the views over the surrounding countryside. Or, head down to the basement beneath the center of the arena and view the rooms where the animals for the fights would once would have been caged (this part is much more intact and accessible than the equivalent in Rome's colliseum).
There are a large number of cafes focused on tourists (complete with polite hawkers who speak several languages) near the entrance of the site. Or, try the cafe within the amphitheatre if you are feeling adventurous. You will probably get better fare at the 'hotel' near the car park.
A supermarket (super-merche) is on the main road between the train station and the amphitheater.
Accomodation options are severely limited. Most visitors to El Jem visit as a day trip from the nearby towns of Sousse or Sfax - this is recommended. Day trips may be part of an organized tour, or just as easily, by train, louge, or taxi.
For those who wish to sleep here, Hotel Julius is next to the train station. It does not come highly recommended.
El Jem's street souvenir pedlers are probably the most rude and intrusive in the whole country. If you're coming by bus they will flock around it before it has parked and will set upon you the very second you exit. [I just visited this site on October 30, 2012 and hereby attest that this statement was/is absolutely untrue.] Remember that you have absolutely no obligation to buy anything, regardless of how insistent they are. If they put their sale item into your hands and ask for money, refusing to take the item when you hand it back to them, just put the item on the ground and walk away. At worse you will get a rude hiss, but they are not a threat, just an annoyance. Just stay calm and ignore them.