It is universally believed that this sculpture represents some symbol, but many different conjectures have been made as to its meaning. One thinks that the column alludes to the solar worship of the Persians; another believes that it is the symbol of the holy fire, and a _pyratheion_ or fire altar, of which the lions are the guardians; a third conjectures that it represents Apollo Agyieus, that is, the "guardian of the gateway." I am of this last opinion, and firmly believe that it is this very same symbol of that god which Sophocles makes Orestes and Electra invoke when they enter their father's house.[110] As to the two lions, the explanation is still more simple. Pelops, son of the Phrygian king Tantalus,[111] migrated hither from Phrygia, where the mother of the gods, Rhea, whose sacred animal is the lion, had a celebrated worship. Most probably, therefore, Pelops brought with him the cultus of the patron deity of his mother-country, and made her sacred animal the symbol of the Pelopids. Æschylus compares Agamemnon himself to a lion;[112] he also compares Agamemnon with Ægisthus as a lion with a wolf.[113] Thus here above the gate the two lions, either as the sacred animals of Rhea or as the symbol of the powerful dynasty of the Pelopids, have been united to the symbol of Apollo Agyieus, the guardian of the gateway. To the left of the sculpture of the lions is a large quadrangular window in the wall. [Illustration: No. 22_a_. The Right and Left Door Posts of the Gate of Lions.] The great gate stands at right angles to the adjoining wall of the citadel, and is approached by a passage, 50 feet long and 30 feet wide, formed by that wall and by another exterior wall, which runs nearly parallel to it, and which forms part of a large quadrangular tower erected for the defence of the entrance.[114] Within these walls the enemy could advance only with a small front of perhaps seven men, exposed on three sides to the arrows and stones of the defenders. A zigzag road on immense Cyclopean substructions, now covered with large blocks which have fallen from the wall, led up to the entrance of the gateway. Leake rightly says that the early citadel builders bestowed greater labour than their successors on the approaches to the gates, and devised various modes of protracting the defence of the interior by numerous enclosures and by intricacy of communication. [Illustration: No. 23. Elevation and Plan of the Postern Gate.] [Sidenote: THE POSTERN GATE.]