The survival of Etruscan habits is clearly seen in the construction of Roman tombs, which existed in enormous numbers outside the gates of the city. Merivale says: "The sepulchres of twenty generations lined the sides of the high-roads for several miles beyond the gates, and many had considerable architectural pretensions." That of Cecilia Metella is a typical example. Here we find a square basement surmounted by a circular tower-like structure, with a frieze and cornice. This was erected about B.C. 60, by Crassus. The mausoleum of Augustus was on a much more extensive scale, and consisted of four cylindrical stories, one above the other, decreasing in diameter as they ascended, and the topmost of all was crowned with a colossal statue of the Emperor. The tomb of Hadrian, on the banks of the Tiber--now known as the Castle of Sant' Angelo--was even more magnificent. This comprised a square base, 75 ft. high, the side of which measured about 340 ft.; above this was a cylindrical building surmounted by a circular peristyle of thirty-four Corinthian columns. On the top was a quadriga with a statue of the Emperor. These mausolea were occasionally octagonal or polygonal in plan, surmounted by a dome, and cannot fail to remind us of the Etruscan tumuli. Another kind of tomb, of less magnificence, was the columbarium, which was nothing more than a subterranean chamber, the walls of which had a number of small apertures in them for receiving the cinerary urns containing the ashes of the bodies which had been cremated. In the eastern portion of the Empire, in rocky districts, the tombs were cut in the rock, and the façade was elaborately decorated with columns and other architectural features. _Domestic Architecture._