Schloss Heroldeck, Protected castle complex in Millstatt am See, Austria.

Schloss Heroldeck is a castle complex in Millstatt am See, Austria, located on the northern slopes of the lake and surrounded by alpine peaks. The property includes two main buildings that provide accommodations ranging from dormitory rooms to private suites with individual bathrooms.

Schloss Heroldeck was built in 1912 as a summer residence for the Viennese paper manufacturer Ludwig Friedrich Musil Edler von Möllenbruck, designed by architects Hans Prutscher and Anton Lerchbaumer. After Austria's annexation by Nazi Germany, the family had to sell it to the NSDAP for 100,000 Reichsmark. From 1938 it served as a Gauführerschule for Carinthia; Else Bormann, Martin Bormann's half-sister, lived there until 1945, and Field Marshal Albert Kesselring stayed briefly. After 1945 it housed British troops and denazification proceedings, later becoming a children's home. In 1988 the evangelical Calvary Chapel bought it as a conference centre.

The castle functions today as a gathering place for church groups and communities that hold their meetings and courses here. Visitors can observe how people use the space for shared activities and spiritual meetings.

The property sits directly on the lake at an elevated position with views toward the mountains, allowing visitors to enjoy the landscape from multiple vantage points. The two residential buildings are connected by pathways and offer different accommodation options depending on visitor needs.

The transformation from a purely historical structure into a modern education center with a religious focus occurred without demolishing the original building fabric. This shows how old architecture can take on new purposes while keeping its essential structure intact.