North Sentinel Island
North Sentinel Island, located in the Bay of Bengal, is not extreme for its geography but for its inhabitants. Sometimes referred to as "the most isolated people in the world," the Sentinelese are an indigenous group of about 50-400 individuals who appear to be pre-Neolithic (they are still in the Stone Age, technologically speaking). They've remained so untouched by civilization because they don't take to kindly to outsiders, and have attacked and even killed visitors to the island. The Indian government has given up hope of diplomatic relations with the Sentinelese, and they remain undisturbed on North Sentinel Island to this day, doing whatever pre-Neolithites do.