The capitolium (or Capitoline Temple), a magnificent temple to Jupiter, Juno and Minerva (begun ca 160 CE), was built on a high podium to the south-west of the town. It has approximately the same dimensions as the Pantheon in Rome.

Founded by Trajan in AD 100 as a colony for army veterans, the Colonia Marciana Traiana Thamugadi, and built by soldiers stationed at Lambaesis. Although its plan is overwhelmingly military, there is little doubt that Thamugadi was intended to be a town, not a military base. Its square shape comprises a grid of 111 blocks, each 20 sq. m; most were subdivided into properties for the individual settlers, while a good number were given over to public buildings. Following a Byzantine period, it was sacked by the Berbers in the 7th century and abandoned. The encroachment of the Sahara on the ruins was ironically the principal reason why the town is so well preserved. Because no new settlements were founded on the site after the 7th century, the town was partially preserved under sand up to a depth of approximately one meter until it was excavated in 1881. Designated a World Heritage Site by UNESCO in 1982.