Architects generally criticise this construction adversely, for “if, on the one hand, the engaged columns might be supposed to serve as buttresses and thus become a useful decoration, it must be admitted, on the other, that the projecting entablatures carried from column to column do more harm than good as regards the solidity of the building. [The architrave having no longer the force of the Greek lintel, being composed of several blocks supported by the arch below.] The Romans, however, did not always falsely apply the true principles of architecture. In the arena of Nîmes, for instance, the two superposed orders which serve as buttresses between the arcades of the two stories on the exterior of that building, are real buttresses. The lower order is composed of projecting piers, the upper order of engaged columns; the cornices follow the contour of each pilaster or column and do not form those projecting belts which are placed so clumsily and uselessly around such buildings as the theatre of Marcellus and the Colosseum of Rome.”[4] [4] Viollet le Duc. This amphitheatre was commenced by Vespasian and continued under Titus, who dedicated it in the year 80 A.D. In the ninth century it was half destroyed, and subsequently became a quarry, from which materials were extracted for the construction of the Farnese palace and other buildings. A large part, however, is standing to-day, having been rescued from total destruction by order of Pope Benoit XIV. There are celebrated remains of amphitheatres at Verona, Pola, Capua, Arles, and Nîmes. Circuses and Naumachias belong to the same class of buildings, the one serving for chariot and other races, and the other for naval combats. The arena in each was oval in plan and from it rose the successive tiers of broad steps upon which the seats were ranged. At the top a portico decorated with statues enclosed the whole building. The Circus Maximus was the most important of these, containing numerous splendid statues and obelisks, and covering a vast area. The aqueducts of ancient Rome stretched for miles across the Campagna. The channel in which the water flowed was supported by one or more arcades, superposed according to the height required. These arcades consisted of round brick arches carried on substantial piers, and were placed where possible upon the highest elevations of the country they traversed. At intervals wide basins were provided for the collection of sediment, and reservoirs received the water at their termination. From the latter pipes supplied the baths and private dwellings. In France the famous Pont du Gard is a portion of an immense Roman aqueduct formed of three rows of arcades, which supplied the city of Nîmes. Bridges were constructed on the same principle; the arches increasing their span according to the depth of the piers upon which they rested, being generally of two stories, the upper one having double the number of piers.