The Black Sea is a marginal sea of the Atlantic Ocean, lying between Europe and Asia. It is connected to the Mediterranean via the Bosphorus Strait, the Sea of Marmara, and the Dardanelles. A unique geographical feature of the Black Sea is its 'meromictic' nature; the upper layers of water do not mix with the deeper, oxygen-depleted (anoxic) layers. This means that organic matter, including ancient shipwrecks, can be perfectly preserved for thousands of years at the bottom. It receives water from major European rivers like the Danube, Dnieper, and Don. Historically, it was a vital region for Greek colonies and later the Ottoman Empire. Today, it is a significant geopolitical zone for energy transport and regional security.