During the 10th and 11th centuries, it became the largest and most powerful state in Europe. It laid the foundation for the national identity of Ukrainians and Russians. Kyiv, the capital of modern Ukraine, became the most important city of the Rus'. In 12th–13th centuries on efforts of Yuri the Long Armed, in area of Zalesye were founded several cities similar in name as in Kievan Rus' such as Vladimir on the Klyazma/Vladimir of Zalesye (Volodymyr), Galich of Merya (Halych), Pereslavl of Zalesye (Pereyaslav of Ruthenian), Pereslavl of Erzya.