Trastevere never got Haussmannized. The lanes between Viale di Trastevere and the river still follow their medieval lines — narrow enough that direct sun only reaches the cobbles for an hour either side of solar noon. The ochre walls stay cool into the afternoon, and the ivy over the trattoria doors is load-bearing shade.
These picks stay off the viale (wide, tram-lined, hot) and inside the lane grid. Santa Maria’s piazza is the sunny exception — cross it on the north side where the church shadow falls.