Stretching across the borders of five nations including Russia, Iran, Kazakhstan, Azerbaijan, and Turkmenistan, the Caspian Sea holds the title of the world's largest lake by surface area. Despite its name, it exhibits characteristics of both a lake and a closed inland sea, containing approximately 78,200 square kilometers of water. Experts from the International Hydrological Institute highlight the Caspian’s pivotal geographical and environmental status, underscoring its crucial influence on regional biodiversity and climate patterns. Recent assessments reveal fluctuating water levels that threaten coastal ecosystems and local economies dependent on fisheries and oil extraction. According to renowned geographer Dr. Elena Morozova, these changes not only reflect climatic trends but also complex geopolitical interactions surrounding resource management. The Caspian Sea's legal status remains a contentious issue, with riparian states negotiating usage rights and environmental protections. Experts emphasize the need for multinational cooperation to address pollution, habitat degradation, and sustainable development. The International Caspian Alliance recently convened to discuss frameworks that could harmonize scientific research, economic interests, and ecological preservation. As one of the planet’s largest inland water bodies, the Caspian Sea embodies both natural grandeur and a delicate geopolitical balance. Looking ahead, safeguarding the Caspian Sea requires innovative policies that consider hydrological science and international diplomacy. Its vast expanse and unique characteristics make it a focal point for understanding inland waters' roles in global environmental and political dynamics.