=315. Public Buildings upon the Campus Martius.=--Out of the lofty trees, however, there rise still loftier structures. Two of the great public thermæ, those of Nero and Agrippa, are here upon the Campus Martius. In this region, also, are three of the principal theaters, that of Pompeius, accommodating some 25,000 people, and two others (Theaters of Marcellus and Balbus) only slightly smaller. Here is the Flaminian Circus and the Amphitheater of Taurus for those horse races and gladiator fights which do not demand the huge Circus Maximus or Flavian. Here again is the golden-roofed Pantheon and a great number of other temples to such ill-assorted gods as the Egyptian Serapis and Isis, Neptune, Minerva of the Campus, and the old Latin goddess Juturna. Notable, too, are the triumphal arches raised across several of the broad avenues. You can in fact wander on across this region from one marvelous structure to another until the eye and brain become weary trying to enumerate, much more to comprehend the succession of buildings every one of which is a triumph of marble and of sculpture. Pressing on to the marge of the Tiber itself, the river above the commercial bridges is seen covered with gay pleasure skiffs plying about under bright flags. The shores are lined with handsome little houses, usually decorated in the doors with potted shrubs or boughs of foliage. Innocent they look in the day time but at night when their windows blaze with lamps they will be veritable traps of iniquity for the enjoyment and then the ruin of the unwary. =316. The Tombs of Hadrian and Augustus.=--Across the river near its main bend, can be noticed the green slopes of the hill of the Vatican uncrowned as yet by any temple of fame, but with the suburban Circus of Nero stretching along its slopes. Directly across the current, also, is rising the enormous circular mass of the Mausoleum of Hadrian, with the derricks and staging still above it swinging to place the last of that galaxy of statues which will look down upon the Tiber.[201] [Illustration: CASTLE OF ST. ANGELO: Tomb of Hadrian in its present state.] We do not cross over to the new structure, but proceeding along the bank to the point where the Via Flaminia continuing “Broadway” bears down beside the river, we see before us the older but very majestic Mausoleum of Augustus. It lifts itself fully 220 feet in the air, its base composed of a vast cylinder coated with sculptured marbles, above which there is heaped a conical mound of earth, planted with evergreen trees, while on the summit stands a colossal statue of its mighty builder himself. Within repose the urns not merely of Augustus, but of nearly all the worthier members of the imperial families. [Illustration: TOMB OF HADRIAN. _Restored after Von Falke._]