An early-medieval fortified settlement was erected here, probably as early as the 6th century. The Gothic castle was built on the hill in the 1st half of the 14th century by Casimir the Great. In 1569, the castle was the venue of the parliamentary session that led to the signing of the Polish-Lithuanian Union of Lublin. To this day, from the entire castle complex only the 13th-century Romanesque tower, known as Donjon, and the Gothic chapel of the Holy Trinity have survived. The present shape of the castle was acquired in the 19th century. It used to be a prison for many years. Today it is the seat of the National Museum in Lublin.