vallis

Vallis, vallis is a third declension feminine i-stem: ablative valle, genitive plural vallium. Some writers give the nominative as valles instead, which is a variant rather than an error.

The surface forms above look wrong until you know why. Manuscripts and older printed editions write u where we print v, because in Latin they were the same letter - so uallis, uallem, ualle are the ordinary spellings in this corpus and carry no different sound. Get used to reading past it. The phrase to know is in hac lacrimarum valle, from the Salve Regina, which put "vale of tears" into every European language. English vale and valley come through French val; Latin also has vallum, a rampart, which is a different word entirely.