In the Hindu epic Ramayana, Nala is the vanara (monkey), who is credited as the engineer of the Rama Setu, a bridge across the ocean between Rameswaram (India) and Lanka, identified with modern-day Sri Lanka, so forces of the god Rama can pass over to Lanka. The bridge is also known as Nala Setu, the bridge of Nala. Sometimes, another vanara called Nila is also credited as the builder of the bridge. Nala is described as the architect of the vanaras. Nala is also described to have fought in the battle between Rama and Ravana, the king of Lanka.
The Ramayana narrates that Sita - the wife of Rama, prince of Ayodhya and avatar of the god Vishnu - was kidnapped by Ravana, the rakshasa (demon) king of Lanka. Rama aided by an army of vanaras (monkeys) reached the end of land and wanted to cross over to Lanka. Rama worships the god of the ocean, Varuna and requests him to make way. When Varuna does not appear before Rama, Rama starts shooting various weapons at the sea, which starts drying up. A terrified Varuna pleads to Rama. Though he refuses to give way, he gives Rama a solution. He tells Rama that Nala, the son of Vishwakarma - the architect of the gods, is amongst his vanara army; Nala has the necessary expertise of an architect, owing to a boon from his divine father. Varuna suggests that Rama construct a bridge across the ocean to Lanka, under the supervision of Nala. Nala volunteers for the task and also comments that the arrogance of the Ocean (Varuna) was tamed by Rama with a threat when love had failed. The vanaras fell mighty trees, and collect logs of wood and giant boulders and cast them in the sea. With the help of the vanara army, Nala completes the 80 miles (130 km) (ten yojana) bridge in just five days. Rama and his army pass over it and reach Lanka, where they prepare to fight Ravana.