CHEBIKA is a mountain oasis in western Tunisia, in Tozeur Governorate. Chebika lies at the foot of the mountains of the Djebel el Negueb and, because of its exposure to the sun, it is known as Qasr el-Shams «Castle of the Sun»
In antiquity, it was once a Roman outpost, named Ad Speculum and later a mountain refuge of the Berber people.
Ad Speculum was civitas of the Roman Province of Africa between 30 BC and 640 AD. Located on the Saharan limes (it) just north of Ad Turres. It was a station on the road linking Tebessa to Gafsa, the Romans used mirrors to communicate with other posts and report possible enemy incursions.