The groundfloor documents the history of the town of St. Goar and the castle with numerous exhibits, archaeological finds, information boards, lithographs and old manuscripts.

They range from the Roman period to the political recovery plans of the 20th century. A model portrays the castle and stronghold around 1600 CE. The information boards provide explanations in German and in English. In the basement, the original barrel vault from 1371, there are artefacts from trade and commerce over the last two centuries, such as cooper tools, machines and equipment from a fretsaw factory and a bookbinder's. The showpiece of this room is the old Rheinfels apothecary.