The Grand Duchy of Lithuania was a significant European state from the 13th to the 18th centuries. It emerged as a powerful entity in Eastern Europe, covering parts of modern-day Lithuania, Belarus, Ukraine, and Poland. The Grand Duchy was known for its diverse population and religious tolerance, fostering a unique cultural blend. At its height, the Grand Duchy of Lithuania was one of the largest countries in Europe. It played a crucial role in regional politics and formed a union with the Kingdom of Poland in 1569, creating the Polish-Lithuanian Commonwealth. This union significantly influenced the history and development of both nations.