Complex sentence: Hrádek u Nechanic was built between 1839 and 1857 as a representative and summer seat by Count František Arnošt of Harach, one of the most important representatives of the Jilemnice dynasty.
Split into simpler sentences: Hrádek u Nechanic was built as a representative and summer seat in 1839-1857 by the count František Arnošt of Harach. He was one of the most important representatives of the Jilemnice dynasty.