The miraculous bridge
The ruins of Thuburnica has really only one thing on offer: The bridge which is still in use, 2 millennia after its construction, with the motor road running over it. It is in such a state that it is easy to miss when driving your car.
The setting of the bridge is rather romantic, with large flowery bushes growing along the small river. It is no problem walking under it.
But that's about it! The military has taken possession of the main parts of the ancient town, including a Byzantine fortress, for which they represent a continuation today. There is also a two-story mausoleum inside the premises, but at least this is quite easy to see from the raod. If you're quick, you can photograph it (second photo).
There is nothing at the site, but Jendouba 35 km southeast has two OK hotels. The standard of Jendouba's food (the best restaurants are at the hotels) is far higher than the hotel rooms. This is especially the case with Hotel Atlas, which has one of Tunisia's best restaurants in terms of food! There are basic restaurants around town.
You can get out here by taking transport from Jendouba of Ghardimaou, then hiking to Kalaat. From there it is just a kilometre to walk. The best is to hire a taxi or have your own vehicle. Then you easily visit Thuburnica as a part of your visit to Chemtou. Chemtou is 10 km east along the the same road.