Hernstein Castle stands at the base of a forested precipice, below the ruin of a 12th century defence tower. Today's castle was built between 1727 and 1730, when Count Karl Joseph von Heussenstein turned a manor house into a stately home with a chapel. In 1798 the estate passed to Baron Heinrich von Müller who created the park and built the dam to form the artificial lake with its island. Archduke Ludwig, a nephew of Emperor Franz II, commissioned Theophil von Hansen who, from 1856-1880, redesigned the castle to become one of the most important Historism (English gothic) buildings in Austria. The wonderfully romantic appearance of the building with its four wings continues to delight and enthral to the present day.
Since the 1960s, the castle has undergone extensive restoration and refurbishment and has been extended with modern, but unobtrusive buildings which today contain the seminar hotel. The historic rooms in the castle are mostly preserved in their original state and are today used as meeting and seminar rooms.