King Kong

Fred Wilson (Charles Grodin), an executive of the Petrox Oil Company, forms an expedition based on infrared imagery which reveals a previously undiscovered Indian Ocean island hidden by a permanent cloud bank. Wilson believes that the island holds vast untapped deposits of oil, a potential fortune which he is determined to secure for Petrox. Unknown to Wilson or the crew, Jack Prescott (Jeff Bridges), a primate paleontologist who wants to see the island for himself, has stowed away on the expedition's vessel, the Petrox Explorer. Prescott reveals himself when he warns the crew that the cloud bank may be caused by some unknown, and potentially dangerous, phenomenon. Wilson orders Prescott locked up, believing him to be a corporate spy from a rival oil company. While being escorted to lock-up, Prescott spots a life raft which, upon inspection, is found to be carrying the beautiful and unconscious Dwan (Jessica Lange). After conducting a thorough background check on the 'spy', Wilson realizes that he is telling the truth and appoints Prescott as the expedition's official photographer, requesting that, due to his medical training, he be present when Dwan revives. When she does regain consciousness, Dwan states that she is an aspiring actress who was aboard a director's yacht, which suddenly and inexplicably exploded.
When the Petrox Explorer finally arrives at the island, the team discovers a primitive tribe of natives who live within the confines of a gigantic wall, apparently built to protect them from a mysterious god-like creature known as Kong. The tribal chief shows an immediate interest in the blonde Dwan, offering to trade several of the native women for her, an offer firmly rejected by Jack. The team then learn that while the island does indeed contain large deposits of oil, it is of such low quality that it is unusable. Later that night, the natives secretly board the ship and kidnap Dwan, drugging her and offering her as a sacrifice to Kong. Appearing from the jungle, Kong, an enormous ape, grabs Dwan from the altar and retreats into the depths of the island.
Although an awesome and terrifying sight, the soft-hearted Kong quickly becomes infatuated by Dwan, whose rambling monologue both calms and fascinates the monstrous beast, taming his baser, more violent instincts. After Dwan falls into mud, Kong takes her back to a waterfall to wash her and dry her with great gusts of his warm breath.
In the meantime, Jack and First Mate Carnahan lead several crew members on a rescue mission to save Dwan. The search party encounters Kong while crossing a log bridge. Enraged by the intrusion into his territory, Kong rolls the huge log, sending Carnahan and all but one of the team plummeting to their deaths. Jack and Boan are the only ones to survive. While Boan returns to the village, Jack presses on looking for Dwan. Kong takes Dwan to his lair. As he starts to undress her, a giant snake appears and attacks them. While the distracted Kong is fighting the snake, Jack arrives and rescues Dwan. After killing the snake, Kong chases them back to the native village. Smashing down the huge gates, he falls into a pit trap that Wilson and the crew have dug, where he is overcome by chloroform.
After learning that the oil cannot be refined, Wilson has instead decided to salvage the expedition by transporting the captive Kong to America as a promotional gimmick for Petrox. When they reach New York City, Kong is put on display, bound in chains with a large crown on his head. When Kong sees a group of reporters pushing and shoving Dwan for interviews, the ape, believing that Dwan is being harmed, breaks free of his bonds. A stampede ensues as panic engulfs the throng, with people crushed and trampled as Kong strides through the crowd. Wilson, trying to flee, loses his footing and is subsequently flattened by Kong's massive foot.
Jack and Dwan, thinking that Kong, like all primates, will not cross water, flee across the Queensboro Bridge to Manhattan. They take refuge in an abandoned Manhattan bar, where Jack notices a similarity between the Manhattan skyline (notably the World Trade Center Twin Towers) and the mountainous terrain of Kong's island. He runs downstairs to call the mayor's office and tells them to let Kong climb to the top of the World Trade Center, on condition that the ape not be harmed. Before Jack can return, Kong discovers Dwan and snatches her from the bar, then makes his way to the World Trade Center with Jack and the National Guard in pursuit.
Kong climbs to the roof of the South Tower of the World Trade Center, where he is attacked by soldiers armed with flamethrowers. Kong manages to evade them with a spectacular leap across to the roof of the North Tower. He rips pieces of equipment from the roof and throws them at the soldiers, killing them when he throws a tank of flammable material. Ignoring Jack's earlier request for safe, live capture, military helicopters are sent in to kill Kong. After ensuring Dwan's safety, Kong fights the attacking helicopters, destroying two of them, while Jack is forced to watch helplessly from the South Tower. Dwan desperately pleads for the military to break off their assault, but the pilots continue firing. The relentless hail of bullets finally brings Kong down; he rolls over the edge of the roof, crashing to the plaza hundreds of feet below. Dwan rushes down to comfort him and tearfully watches him take his last breath. An enormous crowd gathers around the giant ape's body as Dwan is surrounded by photographers. Jack fights his way through the crowd to get to Dwan, but stops short as she is taken away by journalists, despite her cries to him.

Question: What did the native build to protect them from Kong?
Answer: Wall