"DER RING" in German - right, "the ring" in English - is the tradtional name of the (glider) airfield in Ziegenhain, northern Hesse... obviously because the ditch of the old water fortress is a good visible landmark (today used as a prison [JVA Ziegenhain]). The airfield is on the right side of the picture (or south of the fortress), whilst the glider pattern mostly lets you circle down above the prison. :-)