Reading Guide. Hanuman jumped to Lanka using his superpowers, but now Rama and his army of monkey and bears all need to get across the water from the southern tip to India to Ravana's kingdom in Lanka.
Image: The painting below shows two scenes in one frame: you can see the monkeys announcing their plan to Rama and Lakshmana in the center of the image, and then you can see those same monkeys directing the building of the bridge on the left.
Source. Indian Myth and Legend by Donald A. Mackenzie (1913). [200 words]
Rama performed sacrifices to propitiate the God of Ocean, so that the vanar forces might be enabled to pass over to Lanka, but these proved to be unavailing. Then angrily he seized his bow and shot celestial weapons into the bosom of the deep. The earth and the sea were immediately convulsed, and darkness covered the heavens; lightning flashed and thunder bellowed aloud; the mountains began to break in pieces. Rama next seized a fiery dart and threatened to dry up the waters of the sea.
At that moment the King of Ocean rose serenely above the weltering billows in all his splendour, attended by shining water snakes. He addressed Rama with great reverence, reminding him that according to ancient laws he must remain unfordable, but counselling him the while to seek the aid of the vanar chief Nala, son of Vishwakarman, the divine artisan, so that a bridge might be constructed to enable the armies to cross the deep. Then the King of Ocean vanished amidst the waves and the heavens brightened again.
Nala was immediately called upon to give his aid. Assisted by his workmen, this wonderful vanar, whose body was green, constructed a causeway of rocky islands between the mainland and Lanka, and to this day it is called “Rama's Bridge."
Rama meanwhile set up the linga symbol of the god Shiva, and worshipped it on that holy island which hath since been called Rameshwaram.