While much of Earth's land has been mapped via satellite, several regions remain largely "unexplored" due to extreme isolation, harsh terrain, or legal restrictions. The Mariana Trench in the Pacific Ocean is the most significant unexplored frontier, with less than 5% of the deep ocean floor having been mapped in detail. On land, North Sentinel Island in the Bay of Bengal remains a true mystery; the indigenous Sentinelese tribe lives in voluntary isolation and the Indian government strictly prohibits any outside contact, making it one of the last places on Earth where human culture and geography remain unknown to the modern world. Other notable frontiers in 2026 include the Vale do Javari in the Brazilian Amazon, home to the highest concentration of uncontacted tribes, and the Sakha Republic in Siberia, where 40% of the territory lies above the Arctic Circle in permanent permafrost. These locations are protected either by their hostile environments—such as the razor-sharp limestone pinnacles of Madagascar’s Tsingy de Bemaraha—or by government mandates designed to preserve untouched ecosystems and indigenous sovereignty.