The deepest and oldest lake in the world is Lake Baikal, located in Siberia, Russia. It reaches a depth of about 1,642 meters (5,387 feet) and is estimated to be around 25 million years old. Lake Baikal is unique for its crystal-clear waters and a diverse range of endemic species, including the Baikal seal. The lake's ecological importance and breathtaking scenery make it a UNESCO World Heritage site and a popular destination for tourists and researchers.