The world's largest and most mysterious oasis is located in the Nubian Sahara, a massive desert region in Egypt, Libya, Chad, and Sudan. This massive sand desert hides the world's largest and oldest aquifer. Scientists have always been amazed by how long-lasting this oasis is. Therefore, they have looked for krypton 81, which shows how long a source of water lasted and will last. It took about a month for scientists to filter this particle from the oasis water. They are currently conducting research.