In Tunisia, the largest amphitheatre (known as the Coliseum) at Thysdrus (El Djem), with some parts of the second amphitheatre, and the Thapsus amphitheatre have been built with squared stone blocks (opus quadratum). The petrographic and geotechnical analyses of the samples taken from the amphitheatre blocks show that these blocks belong to the Tyrrhenian and to the Mio-Pliocene age. Ancient quarries have been found on the Tyrrhenian dune line between Hiboun and Al Alya, at a distance of 30 km from Thysdrus, from which the Tyrrhenian blocks have been extracted. Concerning the Mio-Pliocene blocks, they have most likely been cut from just one ancient quarry found in the hill of Ksour Essaf. The height of almost all of the measured blocks from the Thysdrus Coliseum is equal to the Punic cubit used at Carthage (50 cm), and the height of the measured blocks from the Thapsus amphitheatre is also equal to the Punic cubit (50 cm), or very close to the Roman cubit (45 cm).