Ancient Roman architecture could penetrate through the clerestory windows. The oldest known basilica, the Basilica Porcia, was built in Rome in 184 BC by Cato the Elder during the time he was Censor. Other early examples include the basilica at Pompeii (late 2nd century BC). After Christianity became the official religion, the basilica shape was found appropriate for the first large public churches, with the attraction of avoiding reminiscences of the Greco-Roman temple form. The Roman circus was a large open-air venue used for public events in the ancient Roman Empire. The circuses were similar to the ancient Greek hippodromes, although circuses served
Ancient Roman architecture panels called "emblemata" were inserted into walls or as the highlights of larger floor-mosaics in coarser work. The normal technique, however, was "opus tessellatum", using larger tesserae, which were laid on site. There was a distinct native Italian style using black on a white background, which was no doubt cheaper than fully coloured work. A specific genre of Roman mosaic obtained the name "asaroton" (Greek "unswept floor"). It represented an optical illusion of the leftovers from a feast on the floor of rich houses. A hypocaust was an ancient Roman system of underfloor heating, used to heat houses with hot