. 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 facade was elaborately decorated with columns and
other architectural features.

_Domestic Architecture._

Of all the palaces which the Roman emperors built for themselves, and
which we know from historical records to have been of the most
magnificent description, nothing now remains in Rome itself that is
not too completely ruined to enable any one to restore its plan with
accuracy, though considerable remains exist of the Palace of the
Caesars on the Palatine Hill. In fact, the palace of Diocletian at
Spalatro, in Dalmatia, is the only remaining example in the whole of
the Roman empire of the dwelling-house of an emperor, and even this
was not built till after Diocletian had resigned the imperial
dignity, so that its date is the early part of the fourth century A.D.
This palace is a rectangle, measuring about 700 ft. one way and 590 ft.
the other, and covers an area of nearly 10 acres. It is surrounded
by high walls, broken at intervals by square and octagonal towers, and
contains temples, baths, and extensive galleries, besides the private
apartments of the Emperor and dwellings for the principal officers of
the household. The architect of this building broke away from
cl