Larger and more imposing in appearance even than the Baths of Caracalla were those of Diocletian, that were capable of accommodating more than 3000 bathers and were built about A.D. 303. The grand hall or tepidarium and the barrel-vaulted entrance portico were most successfully converted in the sixteenth century into the church of S. Maria degli Angeli by Michael Angelo, and one of two circular structures that flanked the encircling wall was later consecrated under the name of S. Bernardo, and is still used as a place of worship.
Next in importance to the Thermæ rank the Amphitheatres of the Roman Empire, in which gladiatorial contests and other trials of skill took place, and without which no town however small was considered complete. Though their detail was almost exclusively borrowed from the Greeks—tiers of arches resting on columns and surmounted by an entablature rising one above the other—their architects managed to impress on them a distinctive character of their own. Finest of all still existing examples is the Flavian Amphitheatre, generally known as the Coliseum at Rome, which occupies the site of the famous Golden House of Nero, and was completed about A.D. 70. It is of elliptical plan, measures some 612 by 515 feet, and was from 160 to 180 feet high. It was capable of containing some 80,000 spectators, and was for a long period the chief meeting-place of the Roman citizens. The exterior is four stories high and consists of a series of three rows of arches, the lowest with Doric, the second with Ionic, and the third with Corinthian capitals, the last surmounted by a row of Corinthian pilasters, forming a fourth story, which is supposed to have been originally of wood and to have been rebuilt in stone considerably later. The groups of seats, which, with the central arena they commanded, were protected from the weather by a moveable awning called the velarium, corresponded with the exterior stories, and to each tier a staircase led up, wide vaulted corridors connecting the various entrances with each other, running round the entire building, the whole producing a most harmonious and pleasing effect.
At Verona, Capria, Pola, and Pezzuoli in Italy, at Syracuse in Sicily, and at Arles and Nîmes in France are remains of important Roman amphitheatres, and of the rarer theatres used for dramatic entertainments must be named the two well-preserved examples at Pompeii, the ruins of the Odeion of Herodes Atticus at Athens, and most ancient of all, the remains of the so-called Theatre of Marcellus at Rome now incorporated with the Orsinii Palace, all which appear to have resembled the Coliseum to a great extent in their general style and decoration.
Of the vast and imposing palaces built or added to by successive Roman emperors, that included audience chambers, basilicas, stadia for athletic games, galleries, state dining-halls, baths, and many suites of apartments for various purposes, there exist unfortunately but a few remains. Nero's Golden House, several of the ruins of which were excavated in the 16th century, and inspired Raphael with some of the decorative details of the loggia of the Vatican, is said to have covered more than a mile of ground, and at one time the whole of the Palatine Hill was occupied by stately edifices, with the Palace of Augustus in the centre and those of Tiberius, Caligula, Nero, Domitian, and Septimius Severus, who greatly added to and modified the work of his predecessors, grouped about them, but all that can now be fully identified are some of the ground plans with a few of the minor details of structure. To atone for this however, much of the Palace of Diocletian at Spalato in Dalmatia, to which that emperor withdrew after his abdication in A.D. 305, which originally formed a small town in itself, is still to a great extent intact, including a temple now used as a cathedral, a gallery 520 feet long by 24 wide, and a few of the covered arcades that originally connected its various parts.
What is left of the so-called Hadrian's Villa at Tivoli near Rome proves that it too was of vast extent, with a great variety of buildings, different suites of rooms having been occupied according to the seasons, and at Pompeii and Herculaneum, thanks to the remarkable preservation of many of the houses in them, notably that named after Pansa, the domestic architecture of the private citizens of the great Roman Empire, of which picturesque arcaded courts were a noteworthy feature, can be well studied, as well as that of the temples, triumphal arches, public baths, &c., all of which greatly resembled those of the Capital.
Whether the Romans were or were not the first people of Western Europe to use the arch, they certainly took a very great delight in it, setting up ornately decorated examples of it at the entrances to their towns, their fora, and their bridges, as well as in commemoration of great victories in war and of the completion of civic enterprises. Most remarkable of those still standing in Rome are the Arch of Titus of one span only, erected in memory of the destruction of Jerusalem by the Emperor after whom it is named; the triple-span arch of Septimius Severus, and the smaller one of Constantine. Though they were rather triumphs of engineering skill than works of architecture properly so called, the fine stone built aqueducts such as those in the Campagna of Rome and at Nîmes must be mentioned here on account of the æsthetic effect of the long rows of lofty arches, and a few words must also be said of the Pillars of Victory, of which that of Trajan at Rome is the most notable still extant, adorned as it is with a spiral of finely sculptured bas-reliefs.
In the early days of the Roman power it was customary to cremate the dead, the ashes being preserved in urns that were ranged in cells known as Columbaria, generally hewn in the living rock. As time went on, however, the Egyptian mode of sepulchre was adopted. Bodies were embalmed and laid in stone or marble coffins which were placed in the basements of tombs of two or more stories, surmounted by round towers with pointed or circular roofs. Of these complex resting-places of the dead the finest now in existence is the Mole or Mausoleum of Hadrian, known as the Castle of S. Angelo, at Rome, which is some 300 feet high and was originally encased in marble. No burial was allowed within the walls of a Roman city, but the approaches were generally lined with tombs as at Rome, at Pompeii, and elsewhere, most of them, though on a smaller scale, of a similar plan to that of Hadrian.