The Acropolis rock with its characteristic trapezoidal shape, dominates the city of Athens, at an altitude of 157 m. The uncovering and restitution of its monuments has been gradually accomplished, since 1834. The main visible monuments of the archaeological site were built during the Classical period, in the second half of the 5th c. B.C., in the framework of the Periclean building program. It is about the Propylaia, the monumental entrance of the classical Acropolis, the Parthenon, doric temple dedicated to goddess Athena and major achievement of the ancient Greek architecture, the Erechtheion, in whose interior space very ancient cults and memories of the city were hosted, and the ionic temple of Athena Nike on a prominent position to the south of Propylaia. Cults devoted to fertility and vegetation performed in open-air sanctuaries and cavernous openings in the rock developed on the North Slope. Among the site's most important monuments are the Klepsydra spring, the three caves dedicated to the cults of Apollo, Zeus and Pan and the Sanctuary of Aphrodite and Eros. A monumental cave dedicated to the nymph Aglauros dominates the East Slope. From the archaic times on, the establishment of important sanctuaries and theatrical buildings on the south side [South Slope] of the Acropolis gave great religious, cultural and spiritual significance. Among the site's most important monuments are the Sanctuary of Asclepios, the Sanctuary and the Theatre of Dionysus Eleuthereus. In the 2nd century A.D., on the western edge of the area, Herodes Atticus built the magnificent Odeion in memory of his wife, Regilla.