magnificent of these, certainly the richest in detail (Fig. 44). Very remarkable was the double temple of +Venus and Rome+, east of the Forum, designed by the Emperor Hadrian about 130 A.D. (Fig. 53). It was a vast pseudodipteral edifice containing two cellas in one structure, their statue-niches or apses meeting back to back in the centre. The temple stood in the midst of an imposing columnar peribolus entered by magnificent gateways. Other important temples have already been mentioned on p. 91. Besides the two circular temples already described, the temple of Vesta, adjoining the House of the Vestals, at the east end of the Forum should be mentioned. At Baalbec is a circular temple whose entablature curves inward between the widely-spaced columns until it touches the cella in the middle of each intercolumniation. It illustrates the caprices of design which sometimes resulted from the disregard of tradition and the striving after originality (273 A.D.). [Illustration: FIG. 54.--PLAN OF THE PANTHEON.] +THE PANTHEON.+ The noblest of all circular temples of Rome and of the world was the +Pantheon+. It was built by Hadrian, 117-138 A.D., on the site of the earlier rectangular temple of the same name erected by Agrippa. It measures 142 feet in diameter internally; the wall is 20 feet thick and supports a hemispherical dome rising to a height of 140 feet (Figs. 54, 55). Light is admitted solely through a round opening 28 feet in diameter at the top of the dome, the simplest and most impressive method of illumination conceivable. The rain and snow that enter produce no appreciable effect upon the temperature of the vast hall. There is a single entrance, with noble bronze doors, admitting directly to the interior, around which seven niches, alternately rectangular and semicircular in plan and fronted by Corinthian columns, lighten, without weakening, the mass of the encircling wall. This wall was originally incrusted with rich marbles, and the great dome, adorned with deep coffering in rectangular panels, was decorated with rosettes and mouldings in gilt stucco. The dome appears to have been composed of numerous arches and ribs, filled in and finally coated with concrete. A recent examination of a denuded portion of its inner surface has convinced the writer that the interior panelling was executed after, and not during, its construction, by hewing the panels out of the mass of brick and concrete, without regard to the form and position of the origin skeleton of ribs. [Illustration: FIG. 55.--INTERIOR OF THE PANTHEON.] [Illustration: FIG. 56.--EXTERIOR OF THE PANTHEON. (From model in Metropolitan Museum, New York.)]