The Polish–Lithuanian Commonwealth was a dual state formed in 1569, uniting the Kingdom of Poland and the Grand Duchy of Lithuania. This political entity was characterized by a unique system of governance that allowed for a significant degree of autonomy for both regions, with a shared monarch and a common parliament. The Commonwealth reached its peak in the 17th century, becoming one of the largest and most populous countries in Europe. It was known for its cultural diversity and religious tolerance, fostering a rich environment for arts and sciences. However, internal conflicts and external pressures eventually led to its decline and partition in the late 18th century.