[Illustration: Fig. 6.] Some of the most characteristic remains of the Roman national taste in architecture are the Mausoleum of Hadrian, and the Tombs of Cæcilia Metella and of Plautius. The ponderous walls of these massive and indestructible marvels of masonry were essentially Roman, but in their external decorations we find a strange combination of foreign designs. The Mausoleum of Hadrian was dressed up with an array of pilasters, columns, and statues, and the Mausoleum of Augustus was covered with terraces and trees, in imitation of the Temple of Belus at Babylon. The most conspicuous among the Roman appropriations of foreign monumental designs were the oriental obelisks which were brought from Egypt, and erected in the Circi at Rome and in front of some of the buildings, and some of which still stand in the piazzas of modern Rome. The remains of eleven of these have been found. The Romans often misused them by placing them alone, and not following the Egyptian method of always setting them in pairs. [Illustration: Fig. 7.] The huge vaulted arches of brick-work and concrete which remain in the Baths of Caracalla, and the Basilica of Constantine, and the massive arches of the Claudian Aqueduct, are the glory of Roman architecture. For the Coliseum, astounding as are its durability and massive grandeur, is not so illustrative of the special Roman development of the use of the arch and of brick-work as are the other great ruins just mentioned. We see embodied in them the indomitable energy which bridged the valleys and tunnelled through the hills, but which possessed no eye for fine proportion of outline or symmetrical and harmonious combination of details. Brickwork was the material in which the characteristic Roman ruins were executed. The Coliseum and the Theatre of Marcellus are dressed in Greek robes, while the brick arches of the aqueducts, and the massive structure of the Baths of Caracalla reflect the peculiar genius and character of the Roman imperial power. [Illustration: Fig. 8.] CHAPTER I. THE PALATINE AND VELIA.