The mansion, also called Lower Manor, was built by the Auerspergs when their castle on Sovič burned down in 1689.
The dominant building with an atrium was built on the foundations of several older buildings and has undergone quite a few reconstructions and changes of purpose to date (main office of the district administration, courthouse, institute, museum). Since 1951, the mansion has been home to the Karst Research Institute, which is the only dislocated unit of the Scientific Research Centre of the Slovenian Academy of Sciences and Arts in Slovenia. The bronze olm on the facade of the building is the work of the academic sculptor Frančišek Smerdu, and the interior of the Institute was also designed by the architect Janko Omahen from Postojna. In 2016, the mansion became the official venue of the Municipality of Postojna for concluding marriages.
The Auerspergs or the Turjak family were the most influential noble family in Slovenia and one of the wealthiest and most influential noble families in the Habsburg monarchy.