GEROLSTEIN, a village and climatic health resort of Ger many, in the Prussian Rhine province, situated on the Kyll, in the Eifel range, 1,240 ft. above the sea, 28 m. north of Trier. The castle of Gerolstein was built in 1115 and is now in ruins. Gerolstein is celebrated for its lithia waters which are largely exported. Pop. (1933) 3,052.