Originally built to support the mercury mine, it now facilitates the town's museum.

With the discovery of mercury in Idrija at the end of the 15th century, mining-related activities soon began to predominantly shape the town and its surrounding areas.

It served as a warehouse until a dedicated storage facility was built in the town at the end of the 18th century.

Its structure is roughly of a rectangular shape, with three defensive towers positioned in the north-west, north-east and south-east corners.

The south side borders on a steep cliff adjacent to Nikova stream, therefore the south-east corner has no tower and is simply an enlarged section of joining walls.