Main article: Sundara Kanda
The Sundara Kanda forms the heart of Valmiki's Ramayana and consists of a detailed, vivid account of Hanuman's adventures. After learning about Sita, Hanuman assumes a gargantuan form and makes a colossal leap across the ocean to Lanka. Here, Hanuman explores the demon's city and spies on Ravana. He locates Sita in Ashoka grove, who is wooed and threatened by Ravana and his rakshasis to marry Ravana. He reassures her, giving Rama's signet ring as a sign of good faith. He offers to carry Sita back to Rama, however she refuses, reluctant to allow herself to be touched by a male other than her husband. She says that Rama himself must come and avenge the insult of her abduction.
Hanuman then wreaks havoc in Lanka by destroying trees and buildings, and killing Ravana's warriors. He allows himself to be captured and produced before Ravana. He gives a bold lecture to Ravana to release Sita. He is condemned and his tail is set on fire, but he escapes his bonds and, leaping from roof to roof, sets fire to Ravana's citadel and makes the giant leap back from the island. The joyous search party returns to Kishkindha with the news.
Sundara kanda in prose from sarga 41 to 53
41) Hanuma thinks within himself that he should implement the fourth strategy for success, viz. open assault with the demons, so as to meet Ravana and his ministers for knowing their designs and strengths. Accordingly, he makes up his mind to damage the royal pleasure-garden attached to the gynaecium at Lanka and then proceeds to do that task.
42) Seeing the devastation caused to the pleasant grove by Hanuma the female-demons ask Seetha who that great monkey was and wherefore he has come and talked to her. Seetha replies that she knows nothing of him. Some of the female-demons go to Ravana and report to him that the pleasant grove attached to the gynaecuium has been destroyed by a mighty monkey and that the monkey went to Seetha and talked to her also earlier to the devastation. They also report that Seetha expressed her ignorance about him. Then, Ravana gets angry and sends some demons called Kinkaras to catch hold of Hanuma. Eighty thousand Kinkaras rush towards Hanuma to catch him. But Hanuma, with his might, kills all Kinkaras with an iron rod. Getting to know of the killings, Ravana again sends Jambumali, the son of Prahasta to catch hold of Hanuma.
43) After damaging the pleasure-grove and after killing the Kinkaras dispatched by Ravana, Hanuma thinks of destroying a sanctuary which is sacred to the guardian-deity of the demons. Hanuma ascends to the top of the sanctuary and after killing the guards posted there, shows his strength by clapping on his arms and by uttering the names of Rama, Lakshmana and Sugreeva in a roaring voice. Hanuma assumes a gigantic form and uplifting a pillar in that sanctuary, he speedily whirls it around and burns the sanctuary by producing a fire, created out of its friction with the other pillars.
44) Ravana sends Jambumali, son of Prahasta, to capture Hanuma. Jambumali attacks Hanuma with his numerous arrows. Hanuma hurls a big rock towards Jambumali, but it fails to kill him. Then, Hanuma throws a big sal tree towards Jambumali and the latter succumbs to it.
45) The seven sons of Prahasta surrounded by a great army rush in speedy chariots upon Hanuma, who is standing on the archy gate way. They discharge a shower of arrows on Hanuma. Then, Hanuma crushes all the enemies, using his palms, feet, fists, nails, chest and thighs only as his weapons. After killing those demons, Hanuma climbs up the archy door-way and takes up his position there again.
46) Ravana sends Virupaksha, Yupaksha, Durdhara, Praghasa and Bhasakarna the five foremost army-generals so as to capture Hanuma. Ravana explains his guess, saying to those five generals that Hanuma may not be an ordinary monkey, but an evil spirit created by Indra the Lord of celestials and asks them to exert a great effort to capture him. Hanuma first kills Durdhara who initially attacks him. He then kills Virupaksha and Yupaksha, by attacking them with a sala tree. Hanuma later kills Praghasa and Bhasakarna, by hurling the top of a mountain on them. After destroying the remaining army together with horses elephants and chariots, he again in returns to the archy door way of the Ashoka groove.
47) Ravana sends Aksha, his own son, to fight against Hanuma. Aksha, along with his army elephants and horses, approach Hanuma and incites him to battle by discharging three sharp arrows. As Aksha discharges his arrows, Hanuma bounces quickly to the sky and smashes Aksha, his chariot and the horses with blows. After killing Aksha, Hanuma returns again to the same archy door-way.
48) Ravana calls Indrajit and asks him to go for a battle against Hanuma. Indrajit wielding a colourful bow quickly in a chariot to face Hanuma in combat. The arrows discharged by Indrajit are made ineffective by Hanuma, through his peculiar skill of maneuvering them like a wind-god. Realizing that Hanuma cannot be slain, Indrajit merely takes him captive by discharging the unfailing missile presided over by Brahma, the creator. Hanuma falls on the ground motionless. The demons tie him with ropes and drag him to the presence of Ravana. Hanuma yields to their operation of capture, even though capable of aborting it, eager as he was to meet Ravana.
49) Hanuma sees well-adorned Ravana, who is seated on a well-decorated throne of crystal. He is surrounded by four ministers viz., Durdhara, Prahasta, Mahaparshva and Nikumbha. Surprised to behold the splendor and glory of Ravana, Hanuma believes that he could even rule heaven along with Indra, but for his gross unrighteousness, which pulled him down.
50) As instructed by Ravana, Prahasta his chief minister inquires of Hanuma as to who he was and also his motive in destroying the pleasure-garden as also killing the demons. In reply, Hanuma says that he destroyed the pleasure-garden in order that he might be taken captive and dragged to the presence of Ravana, whom he was eager to see and was forced in self-defense to kill those who stood in his way. Finally, he declares himself to be a messenger of Rama and adds that, though he was incapable of being bound by a missile presided over by Brahma, he surrendered to it only in order to see Ravana in person.
Hanuma narrates the story of Rama, who on command from his father, went on exile to Dandaka forest along with Seetha, who was later borne away by Ravana through the sky over Rishyamuka mountain. Hanuma adds that Rama, while searching for Seetha at Mount Rishyamuka, happened to meet Sugreeva and made friendship with him. Hanuma also tells the story about Rama installing Sugreeva in the throne, after killing Vali and about Sugreeva promising Rama to get Seetha searched. Celebrating the glory of Rama, Hanuma points out to Ravana that if he wished to survive he should give back Seetha to Rama and that he should be prepared for the worst if on the other hand he refuses to do so.
52) Hearing the harsh words of Hanuma, Ravana orders him to be killed. Vibhishana, however, advises Ravana to desist from the dastardly act, pointing out that the killing of an envoy is forbiddenaccording to religious scriptures.
53) As ordered by Ravana, the demons wrap up old rags around Hanuma's tail, pour oil to it and burn it with fire. The demons tie Hanuma with ropes and conduct ihm to walk down the entire city, proclaining to the citizens of Lanka saying that Hanuma is a spy. The female-demons inform Seetha about the burning of Hanuma's tail and making him move around the city by demons. Then, Seetha starts praying the fire-god to do good to Hanuma. In response to her prayers, fire-god makes Hanuma feel cool with his burnign tail. Then, Hanuma approaches the city-gate of Lanka, takes an iron-rod from the arched door of the gate and kills all the security-guards there.