Pliny says (31.2) that “Tungri, a city of Gallia, has a famous fountain, sparkling with many bubbles; and it has a smack of iron, which is not perceived until after it is drunk: it purges the body, drives away tertian fevers, and disperses calculi.
The same water becomes turbid if fire is applied to it, and finally grows red.” Civitas is the whole territory of the Tungri, whence the modern town of Tongern,
in Belgium; and it is generally supposed that this “famous fountain” is the springs of Spa,
which are south. east of Liège.
This would give to the territory of the Tungri a considerable extension; perhaps, however, not more than it had. No place suits the description of Pliny so well as the waters of Spa.