After Pistoia, Beatrice visits Euthanasia at Valperga in September, under the pretence of asking for alms in aid of her pilgrimage. Euthanasia convinces her to enter, but she only stays for a short dialgoue before leaving for Rome (273-6).
I based my placing of Valperga on these passages:
"The road that led from Lucca to Valperga struck directly across the plain to the foot of the rock on which the castle was built. This rock overhung the road, casting a deep shade; and projected, forming a precipice on three sides; the northern side, on the foot of which the Sercio flowed, was disjoined from the mountain by a ravine" (140).
"The Castle of Valperga was situated on a rock, among the mountains that bound the pass through which the Serchio flows, and commanded the northern entrance to the Lucchese territory." (283) 
“[T]he abrupt and isolated rock on which the castle of Valperga has stood ... formed one of the sides of the chasm which the spirits of creation had opened to make free the course of the Serchio.” (416)