On each side of the arch are some remains of the branch aqueduct, which brought water from the Aqua Marcia to the Baths of Caracalla, and it is natural to conclude that this arch carried the aqueduct over the Via Appia, and was built by Caracalla for that purpose. The costly nature of the materials used has, however, induced most topographers to reject this explanation, and to assume that the arch is one of the three mentioned by the Notitia in the first region, as built in honour respectively of Drusus, Trajan, and Verus. The composite capitals seem to point to the earliest date of these three, and as the building bears a resemblance to a representation of the Arch of Drusus, which has been discovered upon a coin,[120] the arch has been thought identical with that erected to Drusus, the father of Claudius, mentioned by Suetonius. [Sidenote: Sessorium and Amphitheatrum Castrense.] Two ruins standing near the Basilica of S. Croce in Gerusalemme may be reckoned as belonging to the district of the Cælian Hill They are called by the topographers the Sessorium and the Amphitheatrum Castrense. The first of these consists of a ruin built of brick, containing a large semicircular apse with round-headed windows, from which two walls project. No excavations having been made in order to ascertain the further extent of the buildings, any opinion formed as to their purpose must necessarily be highly uncertain. The most probable conjecture which has been made is that they are the ruins of a tribunal called the Sessorium. Such a court of justice is mentioned by the Scholiast on Horace as situated on the Esquiline near the place where criminals and paupers were buried. Further notices of the same name as applied to an edifice in the neighbourhood of the Basilica of S. Croce are to be found in Anastasius’s Life of S. Silvester, and in a fragmentary history of certain passages in the Life of Theodoric, printed at the end of the work of Ammianus Marcellinus. Theodoric is there said to have ordered a criminal to be beheaded in palatio quod appellatur Sessorium, using the same phrase which Anastasius also employs. The authors of the Beschreibung Roms supposed that this ruin was the Nymphæum Alexandri of the Notitia, but this has been disproved by Becker, who shows that the Nymphæum was near the Villa Altieri.