It has been suggested that this refers to the well-known waters of Spa in the province of Liège,[REF] or else to waters found at Tongeren, which are suitably iron-bearing, and today referred to as the "Plinius bron" [REF].
Both Pliny and Ptolemy's Geography are unclear concerning the exact position of the Tungri but are understood as placing them east of the Scheldt, and to the north of the Arduenna Silva (Forest of Ardennes), along the middle and lower valley of the Mosa (Meuse River).