Largest underground lake on Earth : Far below the surface of southern Albania, scientists have confirmed the existence of a vast underground lake hidden inside a cave system near the Greek border. Known as Lake Neuron, the turquoise body of water is now considered the largest underground thermal lake currently known on Earth. The discovery reveals that an enormous landscape has been quietly existing beneath the ground, unnoticed by most people, while life continued as normal above it, as per a Eco News report.