§356. The Coliseum.--The Flavian amphitheater (§352) is the best known of all the buildings of ancient Rome, because to a larger extent than others it has survived to the present day. For our purpose it is not necessary to give its history or to describe its architecture; it will be sufficient to compare its essential parts with those of its modest prototype in Pompeii. The latter was built in the outskirts of the city, in a corner in fact of the city walls (§353); the coliseum lay almost in the center of Rome, the most generally accessible of all the public buildings. The interior of the Pompeian structure was reached through two passages and by three stairways only, while eighty numbered entrances made it easy for the Roman multitudes to find their appropriate places in the coliseum. Much of the earlier amphitheater was underground; all of the corresponding parts of the coliseum were above the level of the street, the walls rising to a height of nearly 160 feet. This gave opportunity for the same architectural magnificence that had distinguished the Roman theater from that of the Greeks (§326). The general effect is shown in Fig. 162, an exterior view of the ruins as they exist to-day. [Illustration: FIGURE 163. INTERIOR OF COLISEUM] §357. The interior is shown in Fig. 163. The form is an ellipse with axes of 620 and 513 feet, the building covering nearly six acres of ground. The arena is also an ellipse, its axes measuring 287 and 180 feet. The width of the space appropriated for the spectators is, therefore, 166½ feet all around the arena. It will be noticed, too, that subterranean chambers were constructed under the whole building, including the arena. These furnished room for the regiments of gladiators, the dens of wild beasts, the machinery for the transformation scenes that Gibbon has described in his twelfth chapter, and above all for the vast number of water and drainage pipes that made it possible to turn the arena into a lake at a moment's notice and as quickly to get rid of the water. The wall that surrounded the arena was fifteen feet high with the side faced with rollers and defended like the one at Pompeii with a grating or network of metal above it. The top of the wall was level with the floor of the lowest range of seats, called the _podium_ as in the circus (§337), and this had room for two or at the most three rows of marble thrones. These were for the use of the emperor and the imperial family, the giver of the games, the magistrates, senators, Vestal virgins, ambassadors of foreign states, and other persons of consequence. [Illustration: FIGURE 164. SECTION OF COLISEUM]