he Acropolis, which in Greek means "the high point of the city," is, without a doubt, the most popular attraction of Athens.  Its rich history, famous antiquities, the celebrated museum, views of Athens, and the ease of access bring thousands of tourists.  The site is particularly beautiful early in the morning or late in the afternoon, when the crowds don't obstruct your vision.  Since the Acropolis is undergoing a thorough restoration, the beautiful temple of Athena Nike (447-427 B.C.) is not represented in my photographs.  The Parthenon (ill. 1),  designed by Phidias, built by Kallikrates and Iktinos between 447 and 438 B.C., continues to be the best example of Greek architectural genius.  It is a masterpiece of mathematical calculations and optical illusions.  The columns lean slightly inward and widen in the middle (entasis) to counteract an illusion of being concave.  The corner columns are slightly thicker, otherwise they would have seemed smaller and thinner than the rest. The building's width to length ratio, as well as the ratio between the diameter of each column and the distance between them was set at an ideal number 4:9.  The temple's floor and steps rise slightly in the middle, creating an illusion of a perfectly straight line. All these "tricks" make the building feel light, balanced, and harmonious. The Propylaea (ill. 4, 6), a monumental entrance to the Acropolis, was begun in 437 B.C. It was an imposing structure, with rooms and halls attractive enough to be converted later into the residence of a bishop, the Frankish dukes of Athens, the Florentines, and the commander of the Turkish garrison.  The Beulé Gate (ill. 5), named for a French archeologist who discovered it in 1853 under a protective wall, is a 3rd-century A.D. Roman addition, constructed after the attack of the Heruli in 267 to provide a better defense and to replace the ceremonial ramp built by Pericles. Today, it serves as an exit from the Acropolis Hill and provides an interesting frame for a photograph of the Propylaea.  Perhaps the most beautiful temple on the Acropolis, the Erechtheion  (ill. 7-9), with its south porch supported by the six Caryatids (all modern copies), was constructed between 421-406 B.C., by Philokles.  The Erechtheion's plan was quite complex because it had to accommodate a number of earlier buildings. Finally, the Odeion of Herodes Atticus (ill. 2-3), a theatre with an elaborate multi-tiered colonnade enclosing the stage, was built in the 2nd century A.D. and  partially rebuilt in modern times because of its phenomenal acoustics.  The theatre is famous for musical and theatrical performances.