Role of three cities in Ramayana
The inner significance of the Sita-Rama story will be clear when we consider the role of the three cities in the Ramayana. First comes Mithila. Emperor Janaka was its ruler. He was a Brahmajnaani (one who possesses knowledge of identity of individual self with the cosmic being) who had renounced everything. Like water on a lotus leaf, he was completely detached, with no concern for worldly things. Having no children of his own, he brought up with great love a foundling (Sita). There were two powerful entities in his kingdom' Siva's bow and Sita. Once, while engaging in play, Sita lifted the giant bow of Siva with astonishing ease. Struck by this feat, Janaka decided that Sita should be given in marriage only to one who could handle Siva's bow and be worthy of Sita's hand. With this resolve, he invited princes for Sita's svayamvara (self selection of a husband by the bride herself). Rama arrived and lifted Siva's bow as lightly as Sita had done. Janaka realised that Rama and Sita were well matched in every respects---beauty, character and strength. Sita was no ordinary woman. She was the embodiment of Maha Maya (supreme divine illusion). Rama acquired Maha Maya as his mate. Sita, for her part, sought oneness with the Atma principle represented by Rama. The marriage of Rama and Sita represents the association of the Atma and the Maya. It is in this combined form of Atma and Maya that Rama entered Ayodhya. "Ayodhya" means "invincible". Its ruler was Dasaratha. Dasaratha means one who has made his ten indriyas (sense organs) the five organs of action and the five organs of perception—his chariot. Allegorically, this means that Dasaratha represents the body, with its ten organs. These sense organs are related to the three gunas (qualities) Satwa, Rajas, Tamas. Dasaratha's three wives--- Kausalya, Sumitra and Kaikeyi---symbolise these three gunas.
Source: Discourse in the Prashaanthi Mandir on 7-4-1987.