Zeus hurled a thunderbolt which destroyed the chamber of Semele at Thebes and the place was an ἄβατον in the time of Pausanias (IX, 12, 4). When Zeus struck Erechtheus with a thunderbolt, the spot on the Acropolis where the lightning struck may likewise have become an ἄβατον. It is interesting to note that at Olympia, Pausanias (V, 14, 7) saw the foundations of the house of Oenomaus and two altars, one to Zeus Herkeios which Oenomaus seems to have built, the other to Zeus Keraunos erected later, after the thunderbolt had destroyed the house. The persons and palaces of mythical kings appear to have been a favorite mark for the thunderbolt of Zeus. The tradition preserved in Hyginus is an illustration, and tempts one to seek in the vicinity of the Erechtheum for some record of the thunderbolt.
And so too does the notice of the scholiast (after Apollodorus) on Sophocles, _Oed. Col._, 705, who says that near the Academy there was an altar to Zeus Kataibates who was also called Morios: ἐστὶν ὅ τε τοῦ καταιβάτου Διὸς βωμὸς ὃν καὶ Μόριον καλοῦσιν τῶν ἐκεῖ μοριῶν παρὰ τὸ τῆς Ἀθηνᾶς ἱερὸν ἱδρυμένων. That Zeus Kataibates should have been called Μόριος (μορία) points to some relation with Athena and the olive which may have had its origin on the Acropolis. Does this double name simply mean that Zeus "of sleepless eye" used lightning (καταιβάτης) to avenge sacrilege which one committed when he violated a sacred olive (μορία) as Miss Harrison, _Mythology and Monuments of Ancient Athens_, p. 599, suggests, or is the key to the explanation furnished by a passage in Pausanias (IX, 12, 4)? Pausanias records the tradition that at the time Zeus hurled the thunderbolt which destroyed Semele and her bridal chamber a log fell from heaven which Polydorus adorned with bronze and called Dionysus Cadmus. Perhaps the ancient image of Athena, the xoanon of olive wood, which fell from heaven, fell at the time Zeus smote Erechtheus, just as the wooden image of Dionysus Cadmus fell when Zeus destroyed Semele. If so, then Zeus Kataibates, by bringing to earth a piece of sacred olive (μορία) very naturally acquired the name Zeus Morios.
What known altar to Zeus in the vicinity of the Erechtheum could have been erected to him in his capacity as καταιβάτης? There was an altar of Zeus Herkeios under the olive in the Pandroseum. This, however, cannot have served as an altar of Zeus Kataibates because these were two distinct phases of the Zeus cult. Pausanias found near the ruins of the palace of Oenomaus at Olympia an altar to Zeus Herkeios and another to Zeus Keraunos (Kataibates). Before the entrance to the Erechtheum Pausanias found an altar to Zeus Hypatus beside the sacred indentations in the rock which lay beneath an opening in the roof, and this is none other than the altar to Zeus Kataibates.