The Celtic hill fort of Otzenhausen is one of the biggest fortifications the Celts ever constructed.
It was built by Gauls of the Treveri tribe, who lived in the region north of the fort. The fort is located on top of the Dollberg, a hill near Otzenhausen in Germany, about 695 m above sea level. The only visible remains are two circular earth ramparts, covered with stones.
Wikipedia https://en.wikipedia.org/wiki/Hillfort_of_Otzenhausen
Address 66620, Germany
Coordinates 49°37'17.395" N 7°0'9.111" E