<P> There was considerable local variation in style, as Roman architects often tried to incorporate elements the population expected in its sacred architecture . This was especially the case in Egypt and the Near East, where different traditions of large stone temples were already millennia old . The Romano - Celtic temple was a simple style for small temples found in the Western Empire, and by far the most common type in Roman Britain . It often lacked any of the distinctive classical features, and may have had considerable continuity with pre-Roman temples of the Celtic religion . </P> <P> Roman theatres were built in all areas of the empire from Spain, to the Middle East . Because of the Romans' ability to influence local architecture, we see numerous theatres around the world with uniquely Roman attributes . </P> <P> These buildings were semi-circular and possessed certain inherent architectural structures, with minor differences depending on the region in which they were constructed . The scaenae frons was a high back wall of the stage floor, supported by columns . The proscaenium was a wall that supported the front edge of the stage with ornately decorated niches off to the sides . The Hellenistic influence is seen through the use of the proscaenium . The Roman theatre also had a podium, which sometimes supported the columns of the scaenae frons . The scaenae was originally not part of the building itself, constructed only to provide sufficient background for the actors . Eventually, it became a part of the edifice itself, made out of concrete . The theatre itself was divided into the stage (orchestra) and the seating section (auditorium). Vomitoria or entrances and exits were made available to the audience . </P> <P> A Roman villa was a country house built for the upper class, while a domus was a wealthy family's house in a town . The Empire contained many kinds of villas, not all of them lavishly appointed with mosaic floors and frescoes . In the provinces, any country house with some decorative features in the Roman style may be called a "villa" by modern scholars . Some were pleasure palaces such as those--like Hadrian's Villa at Tivoli--that were situated in the cool hills within easy reach of Rome or--like the Villa of the Papyri at Herculaneum--on picturesque sites overlooking the Bay of Naples . Some villas were more like the country houses of England or Poland, the visible seat of power of a local magnate, such as the famous palace rediscovered at Fishbourne in Sussex . </P>

Why did roman architects frequently use the arch vault and dome in construction