The ancient Egyptians, hemmed in by deserts, relied less on walls than on the defenses provided by nature. Thus relieved from the necessity of building fortifications, they expended their energies in such monumental works as the Great Pyramids and temples that embody a civilization which for at least nine thousand years has been the wonder and the admiration of the world. [Illustration: XII. PLAN SHOWING NERO’S CIRCUS AT ROME (FIRST CENTURY), BASILICA OF ST. PETER (FOURTH CENTURY), AND THE PRESENT CATHEDRAL OF ST. PETER (SIXTEENTH CENTURY). These structures were built at successive epochs, on the same site.] Means of defense having been provided, the desire of mankind for order and magnificence found expression in works of adornment, which were measured only by the love of the citizens for their city, the artistic sense developed among the people, and the means at their disposal for carrying out their conceptions. Nowhere else have these conditions been combined as they were in Athens during the days of Pericles. Year by year the patient excavator is bringing to the light the massive walls by which the early Athenians protected their citadel against the invader; and when security had been obtained and the tribute of the allies had accumulated in the treasury, the Greek passion for beauty found expression in public buildings which through the ages have placed the Acropolis at Athens among the world’s famous places. Plutarch lays emphasis on the fact that undertakings, any one of which singly might have required for its completion several successions and ages of men, were every one of them accomplished in the height and prime of one man’s political service. “Pericles’ works,” this same writer asserts, “were especially admired because they were made quickly to last long. For every particular piece of his work was immediately, even at that time, for its beauty and elegance, antique; and yet in its vigor and freshness looks to this day as if it were just executed. There is a sort of bloom of newness upon those works of his, preserving them from the touch of time, as if they had some perennial spirit and undying vitality mingled in the composition of them.” [Illustration: XIII. AN ANCIENT ROMAN CIRCUS, NEAR THE APPIAN WAY. From an etching by Piranesi.]