The Sorgue and Fontaine-de-Vaucluse: We know from Petrarch's other writings (and because of his residence in Vaucluse) that he had a great love for the beautiful Sorgue River in the south of France. It is believed to be the body of water of "Clear, fresh and sweet waters" fame.
The Church of St. Claire, Avignon: Petrarch alludes to "the well-known place [...] where she first saw me" in lines 28 and 30. This is the Couvent de Sainte-Claire in Avignon, where they both grew up.
Laura de Noves. This is the Laura. Though Petrarch doesn't mention her by name in this poem, he does use her first name elsewhere.