In the time of the empire many palaces of the richer classes stood upon the Cælian. Among them we have distinct mention of the houses of Claudius Centumalus, which was visible from the Arx, of Mamurra, and of Annius Verus, in which Marcus Aurelius was born. Tetricus also, the unsuccessful rival of Aurelian, built a magnificent residence on the Cælian, in which, on his readmission to the emperor’s favour, he entertained Aurelian. [Sidenote: Palace of Commodus.] It seems probable, as Bunsen has conjectured, that the Vectilian Palace in which Commodus lived, occupied the part of the Cælian next to the Coliseum. The ruins there consist of arches of travertine, forming a rectangular space upon the northern end of the hill. They are massively constructed, so as to bear a great superincumbent weight, and would be in every way suitable for the terraces of a large imperial villa such as Commodus may have built, when, as Lampridius tells us, he removed from the Palatine, where he found himself unable to sleep, to the house of Vectilius on the Cælian. He was afterwards murdered there. The position may have pleased him from its immediate vicinity to the Coliseum, where he was so fond of superintending the exhibitions, and displaying his own skill in killing wild animals. The story that he had an underground passage made from his villa to the Coliseum is also a strong confirmation of the conjecture of Bunsen, and some additional probability is given to it by the course of the branch aqueduct which leads from the Arch of Dolabella in the direction of this garden, and would certainly be required to supply the luxuries of a large Roman palace. APPENDIX TO CHAPTER VIII. MONUMENTAL ANTIQUITIES IN THE MUSEUMS, PIAZZAS AND OTHER PLACES. Besides the ruins which are still standing in Rome and the Campagna, many historical monuments may be seen in the Roman museums, and in some of the gardens and piazzas. The principal among these are as follows: [Sidenote: Egyptian antiquities.] 1. Numerous Egyptian antiquities were found near the Churches of S. Maria sopra Minerva and that of S. Stefano in Cacco, on the site of the ancient Temples of Isis and Serapis. Of these the most remarkable are the two obelisks, one of which now stands in front of the Pantheon, and the other in the Piazza della Minerva. The statue of Isis, now in the Hall of the Dying Gladiator at the Capitoline Museum, the Egyptian lions on the steps of the Capitol, and the famous statue of the Nile now in the Braccio Nuovo of the Vatican, were also found here. [Sidenote: Bas-reliefs from Arch of M. Aurelius.]