The Lord (Ramacandra) built a floating bridge of stones on the Indian Ocean and reached Lanka, the kingdom of Ravana, who had kidnapped Sita. Later on Ravana was killed by Him, and Ravana's brother Vibhisana was installed on the throne of Lanka
SB Canto 1
The learned brāhmaṇas said: O son of Pṛthā, this child shall be exactly like King Ikṣvāku, son of Manu, in maintaining all those who are born. And as for following the brahminical principles, especially in being true to his promise, he shall be exactly like Rāma, the Personality of Godhead, the son of Mahārāja Daśaratha.
Prajā means the living being who has taken his birth in the material world. Actually the living being has no birth and no death, but because of his separation from the service of the Lord and due to his desire to lord it over material nature, he is offered a suitable body to satisfy his material desires. In doing so, one becomes conditioned by the laws of material nature, and the material body is changed in terms of his own work. The living entity thus transmigrates from one body to another in 8,400,000 species of life. But due to his being the part and parcel of the Lord, he not only is maintained with all necessaries of life by the Lord, but also is protected by the Lord and His representatives, the saintly kings. These saintly kings give protection to all the prajās, or living beings, to live and to fulfill their terms of imprisonment. Mahārāja Parīkṣit was actually an ideal saintly king because while touring his kingdom he happened to see that a poor cow was about to be killed by the personified Kali, whom he at once took to task as a murderer. This means that even the animals were given protection by the saintly administrators, not from any sentimental point of view, but because those who have taken their birth in the material world have the right to live. All the saintly kings, beginning from the King of the sun globe down to the King of the earth, are so inclined by the influence of the Vedic literatures. The Vedic literatures are taught in higher planets also, as there is reference in the Bhagavad-gītā (4.1) about the teachings to the sun-god (Vivasvān) by the Lord, and such lessons are transferred by disciplic succession, as it was done by the sun-god to his son Manu, and from Manu to Mahārāja Ikṣvāku. There are fourteen Manus in one day of Brahmā, and the Manu referred to herein is the seventh Manu, who is one of the prajāpatis (those who create progeny), and he is the son of the sun-god. He is known as the Vaivasvata Manu. He had ten sons, and Mahārāja Ikṣvāku is one of them. Mahārāja Ikṣvāku also learned bhakti-yoga as taught in the Bhagavad-gītā from his father, Manu, who got it from his father, the sun-god. Later on the teaching of the Bhagavad-gītā came down by disciplic succession from Mahārāja Ikṣvāku, but in course of time the chain was broken by unscrupulous persons, and therefore it again had to be taught to Arjuna on the Battlefield of Kurukṣetra. So all the Vedic literatures are current from the very beginning of creation of the material world, and thus the Vedic literatures are known as apauruṣeya (not made by man). The Vedic knowledge was spoken by the Lord and first heard by Brahmā, the first created living being within the universe.
Mahārāja Ikṣvāku: One of the sons of Vaivasvata Manu. He had one hundred sons. He prohibited meat eating. His son Śaśāda became the next king after his death.
Manu: The Manu mentioned in this verse as the father of Ikṣvāku is the seventh Manu, of the name Vaivasvata Manu, the son of sun-god Vivasvān, to whom Lord Kṛṣṇa instructed the teachings of Bhagavad-gītā prior to His teaching them to Arjuna. Mankind is the descendant of Manu. This Vaivasvata Manu had ten sons, named Ikṣvāku, Nabhaga, Dhṛṣṭa, Śaryāti, Nariṣyanta, Nābhāga, Diṣṭa, Karūṣa, Pṛṣadhra and Vasumān. The Lord's incarnation Matsya (the gigantic fish) was advented during the beginning of Vaivasvata Manu's reign. He learned the principles of Bhagavad-gītā from his father, Vivasvān, the sun-god, and he reinstructed the same to his son Mahārāja Ikṣvāku. In the beginning of the Tretā-yuga the sun-god instructed devotional service to Manu, and Manu in his turn instructed it to Ikṣvāku for the welfare of the whole human society.
Lord Rāma: The Supreme Personality of Godhead incarnated Himself as Śrī Rāma, accepting the sonhood of His pure devotee Mahārāja Daśaratha, the King of Ayodhyā. Lord Rāma descended along with His plenary portions, and all of them appeared as His younger brothers. In the month of Caitra on the ninth day of the growing moon in the Tretā-yuga, the Lord appeared, as usual, to establish the principles of religion and to annihilate the disturbing elements. When He was just a young boy, He helped the great sage Viśvāmitra by killing Subahu and striking Mārīca, two demons who were disturbing the sages in their daily discharge of duties. The brāhmaṇas and kṣatriyas are meant to cooperate for the welfare of the mass of people. The brāhmaṇa sages endeavor to enlighten the people by perfect knowledge, and the kṣatriyas are meant for their protection. Lord Rāmacandra is the ideal king for maintaining and protecting the highest culture of humanity, known as brahmaṇya-dharma. The Lord is specifically the protector of the cows and the brāhmaṇas, and hence He enhances the prosperity of the world. Through the agency of Viśvāmitra He was rewarded by the administrative demigods with effective weapons to conquer the demons. He was present in the bow sacrifice of King Janaka, and by breaking the invincible bow of Śiva, He married Sītādevī, daughter of Mahārāja Janaka.
After His marriage He accepted exile in the forest for fourteen years by the order of His father, Mahārāja Daśaratha. To help the administration of the demigods, He killed fourteen thousand demons, and by the intrigues of the demons, His wife, Sītādevī, was kidnapped by Rāvaṇa. He made friendship with Sugrīva, who was helped by the Lord to kill Vāli, brother of Sugrīva. By the help of Lord Rāma, Sugrīva became the king of the Vāṇaras (a race of gorillas). The Lord built a floating bridge of stones on the Indian Ocean and reached Laṅkā, the kingdom of Rāvaṇa, who had kidnapped Sītā. Later on Rāvaṇa was killed by Him, and Rāvaṇa's brother Vibhīṣaṇa was installed on the throne of Laṅkā. Vibhīṣaṇa was one of the brothers of Rāvaṇa, a demon, but Lord Rāma made him immortal by His blessings. On the expiry of fourteen years, after settling the affairs at Laṅkā, the Lord came back to His kingdom, Ayodhyā, by flower plane. He instructed His brother Śatrughna to attack Lavṇāsura, who reigned at Mathurā, and the demon was killed. He performed ten Aśvamedha sacrifices, and later on He disappeared while taking a bath in the Sarayū River. The great epic Rāmāyaṇa is the history of Lord Rāma's activities in the world, and the authoritative Rāmāyaṇa was written by the great poet Vālmīki.