188 metres in length and i56 metres in width, while the arena, measures 86x54 metres. It was apparently the largest amphithe atre in the Roman world.
Near by stands the well proportioned Arch of Constantine which however is largely constructed of materials taken from previous arches. The only sculpture upon it that belongs to Con stantine's day is the very narrow frieze rudely carved in a band about its centre. The other reliefs were taken from structures of the second century and in the use of these the imperial por traits were rechiselled to represent Constantine. North-east of the Colosseum one may enter several rooms of the golden house of Nero,' or rather the private apartments of that emperor. The rooms have been to some extent pfeserved because the walls were later used as substructions for a part of Trajan's baths built at a higher level. Many of the rooms of the palace have recently been excavated and reveal much damaged frescoes and stucco reliefs which represent the best work of its kind at Rome for the period of Nero. It was here, as graffiti on the walls indi cate, that several of the Renaissance painters borrowed themes and designs for the arabesque and "grotesque" decoration so popular when the loggia of the Vatican was decorated.
Several of the massive Thermae (Baths) of ancient Rome are still among the most conspicuous ruins of the city. The first large structure of this type was the one built by Agrippa in 20 B.C. south of the Pantheon. Little now remains of this. More may be seen of the ruins of those constructed by Titus and Trajan (on the grounds of Nero's Domus Aurea), by Caracalla on the edge of the Aventine and by Diocletian (part of which is now used for the national museum). Since these buildings contained, besides the baths, playgrounds, gymnasia, clubrooms and auditoria for immense crowds, the architects who constructed them had to employ all the arts and sciences at their disposal. The central building of Caracalla's baths covers an area of 27o,000sq.f t. ; and the central hall has a clear space of 183x79ft. It is roofed with a solid concrete intersecting barrel vault that rests chiefly on f our massive piers and rises 1 o8f t. from the pavement. It was while solving the problems of such construction that the Roman archi tects made those contributions to their art which have been most frequently studied by recent architects. The baths of Diocletian
have suffered more from time, but the church of S. Maria degli Angeli has preserved two of its great halls. Here may be seen in their most advanced use at Rome good examples of flying and rectangular buttresses, a careful system of thrusts and counter thrusts and of ribbed quadripartite vaulting. A large number of the smaller rooms are used by the Museo delle Terme.
Finally the Subterranean Basilica' discovered near Porta Mag giore in 1917 has proved to be not only one of the best preserved of ancient buildings but one of the most important for the inter pretation of Roman life. Though it seems to have been built be fore the middle of the 1st century A.D. it has the regular basilican form with nave, apse and two aisles. It was built wholly under ground apparently for the purposes of a secret religious sect. The ceilings of the nave, the apse and the aisles are richly adorned with excellent stucco reliefs, the interpretation of which has proved as difficult as would be the explanation of the biblical illustrations of a mediaeval cathedral if we had no copies of the Bible. The most generally accepted view is the one proposed by Cumont, that this basilica was the temple of a Neo-Pythagorean congregation which practised mystic rites of initiation that were not approved of by the imperial authorities, and that the reliefs in question pertain to myths and rites which had been given a symbolic interpretation in the Neo-Pythagorean ritual. But quite apart from their meaning, they now give us the best conception possible of the beauty of Roman interior decoration for the 1st century of the empire. (See Rivoira, Roman Architecture, p. 204.) (T. F.) In the middle ages the population of Rome had dwindled to twenty or thirty thousand inhabitants, who lived huddled together 'Weege, Das Goldene Haus, Jahrb. des Arch. Inst. p. 127 (1913). Tarcopino, La Basilique Pythagoricienne (1927) ; for illustrations 'PP A1Pmnirc Amor Arad hi (Tn1A1 about the strongholds of the barons, and the modern city grew slowly upon the exiguous foundation of a mediaeval town. The first plan for modernizing and improving Rome was that of Pope Julius II., who aimed at the enlargement of the lower city on both sides of the Tiber. Following him, Sixtus V. did his best to develop the upper part of the city by laying out the Via Sistina, from the Trinita, dei Monti to S. Maria Maggiore and Porta S.