From two of the sides of the =Baths of Caracalla= projected long _exhedras_, or semi-circular recesses, furnished with benches, which are supposed to have been the meeting places for the discussion of philosophy and poetry. In fact, the great thermæ were the clubs of the period; the resort of all classes, offering cleanliness to the poor, luxury to the rich, and healthful exercise and opportunity of cultured intercourse between those who desired it. And the highest skill was represented in making the walls of the various chambers and reservoirs impervious to moisture, in conducting and heating the water, and in providing flues for hot air. =Basilica.=--Equally characteristic of Roman life were the _Basilicas_. These structures seem to have been intended at first to relieve the congestion of business in the various fora and to afford quiet as well as protection from the weather, for the transaction of business. The earliest in Rome was erected <small>B.C.</small> 184 by Porcius Cato; hence called the =Basilica Porcia=. Then followed the =Basilica Fulvia=, =Basilica Æmilia=, and =Basilica Julia=, the last being the largest of the five which existed during the reign of Augustus. In <small>A.D.</small> 112, Trajan built the great =Basilica Ulpia= in connection with his forum, and some two hundred years later was erected the vaulted =Basilica of Maxentius= or =Constantine= on the Via Sacra. In all there came to be some twenty basilicas in Rome alone. One great interest of the basilica halls consists in the fact that from them were derived the plan and form of the early Christian churches. It has been conjectured that the plan of a basilica was derived from that of a Greek temple, the cella walls being replaced by ranges of columns, opening into the peristyle where in turn the columns were replaced by side walls. The colonnades thus became aisles to the central nave; the vestibule being retained at one end and later to be called a _narthex_, while at the opposite end an apse projected. Here in the Roman basilica were the seats of the quæstor and his assessors, occupied in early Christian basilica churches by the bishop and presbyters. The interiors of the Roman basilicas present two types of treatment. In the =Basilica of Constantine=, for example, the nave columns were attached to great piers which supported groined vaults, the thrust of which was sustained by walls at right angles to the piers. These walls divided each aisle into three _bays_, corresponding to the three bays of the nave, and over each aisle-bay was a barrel-vault, which, being at right angles to the nave, served as extra support to the nave-vaults. Light was admitted through windows in the side walls of the aisles and also through windows in the upper part of the nave, above the aisle vaults.