The Oder River, also known as the Odra River, is the second-longest river in Poland and the tenth-longest river in Europe. Additionally, the river flows through Germany, the Czech Republic, and Slovakia, and it ultimately empties into the Baltic Sea. Besides Oder and Odra, the river has several other names, including the Moravian Oder, the Upper Oder, and the Silent Oder. The Moravian Oder distinguishes the eastern part of the river, which flows through the historical region of Moravia, while the Upper Oder denotes the upper reaches of the river. And finally, it is also sometimes called the Silent Oder due to its slow and calm flow in some parts.