The vast ruins which remain on the south of the stadium belong chiefly to the works of Septimius Severus, and have long been celebrated as the most picturesque among the Cæsarean relics. The curved wall behind the great exedra, and the numerous passages and chambers which stand near it, seem to have belonged to a bath supplied with water from the branch of the Aqua Claudia, four arches of which are still remaining on the hill below, opposite to the church of S. Gregorio. This was a branch from the Claudian aqueduct, and crossed the valley from the opposite Cælian Hill. [Sidenote: Palatine Belvedere.] The lofty wing of the palace, which extends along the slope of the Circus Maximus, opposite to the Aventine, is reached by a modern bridge from the ruins adjoining the stadium. From the top of this huge ruin a splendid view of the Cælian, the Aventine, and the Alban Hills may be seen, and the spot has been sometimes called the Palatine Belvedere. What the exact nature of the buildings placed upon these lofty ranges of arches was cannot be easily determined, but they correspond in some degree to the arched walls of the side between the arches of Titus and Constantine and to those of the palace of Caligula near the Capitoline, and were mainly intended to raise the imperial saloons to the higher level of the northern end of the hill. Spartianus in his ‘Life of Severus’ says that Severus bestowed particular pains on this part of the Palatine Hill in order to make it the chief entrance to the imperial palace, and that his reason for so doing was to produce an impression of his magnificence upon his African fellow-countrymen, who, when visiting Rome, would naturally enter at this point by the Porta Capena, which was the gate just below. The Septizonium was an imperial building near this part of the hill probably built by Severus, views of the ruins of which are to be seen in the books of the topographers Du Perac and Garrucci who wrote before the end of the sixteenth century, when the Septizonium was pulled down by Sixtus the Fifth.[13] At the western end of the long and lofty ruin, and near the end of the stadium, is a projecting portion of ruined chambers which has been generally supposed to have contained the emperor’s private pulvinar, or box whence he viewed the games in the Circus Maximus. But the construction of this edifice, including its round tower, seems to be of a very late style, and it may have been built as late as the sixteenth century.