The work of excavating the Stadium is not yet completed. It appears that the portico surrounding it originally consisted of cipollino columns, with composite capitals. This was rebuilt in the third century in two tiers, supported with half-columns of brick, coated with slabs of marble, having Ionic bases and Doric capitals. A brick stamp informs us that the Imperial tribune was built in the third consulship of Ursus Servianus, under Hadrian, 134. At the edge of the foot-course, below the portico, was a marble channel to carry off the rain-water. Traces of the spina still remain. The Stadium seems to have been altered into a hippodrome in the time of Diocletian by building elliptical walls upon its surface. The following stamp was found on some of the bricks,--A.D. 500 OFFS R. F. MARCI HIPPODROME THEODORIC REGNANTE DN THEODERICO FELIX ROMA,--evidently some of the repairs ordered by the great king during his six months' visit to Rome. THE EXEDRA, OR ODEUM (27). On the right of the Stadium, for musical performances, with three chambers underneath decorated with fresco work. THE NYMPHÆUM OF MARCUS AURELIUS (30). We claim the honour of having discovered the use of these imposing ruins, whose summit is climbed by many visitors to enjoy the fine view over the Campagna. It was built by the best of the Roman emperors as a large reservoir for the supply of water to the Palatine Hill, acting as the Trevi Fountain does at present. We have traced the specus of the aqueduct to it; and the top is covered with _opus signinum_, the peculiar cement used by the Romans whenever they conducted water. The brickwork shows signs of careful construction; the courses of cement carefully laid between the bricks being of the same thickness as the bricks themselves, seven of which measure a foot. The Nymphæum probably took its name from the female statues which decorated it, handing down the custom of the ancient Romans in peopling the springs with nymphs. It is thus mentioned by Marcellinus (xv. vii. 3):--"The Emperor Marcus built the Nymphæum, an edifice of great magnificence, near the well-known Septemzodium," which was built by Septimius Severus at the corner of the Palatine, where slight traces of it remain; it having been destroyed by Pope Sixtus V. The spot now forms a pleasant terrace, from which a splendid prospect of the southern part of ancient Rome, the Campagna, and the distant Alban Hills may be enjoyed. In fact, a vast study is spread, like a map, before the visitor. THE PALACE OF COMMODUS (25, 29)