Large Cistern I Schlossberg Graz | Graz Tourismus https://www.graztourismus.at/graztourismus/de/sightseeing-kultur/sehenswuerdigkeiten/grosse-zisterne_shg_9415
The Great Cistern on Schlossberg Graz: Built between 1544–1547 as a rainwater reservoir for the fortress, today serving as a fire water reserve.
Graz Tourismus – Harry Schiffer Picture gallery Address