What is the best focal length for Tuscan landscapes?

For Tuscan landscapes, I would choose a 35 mm in full-frame equivalent : it's a versatile focal length for framing the hills without distorting the cypresses or buildings too much. If you only want to take one zoom, a 24–70 mm covers more situations: 24 mm for wide views, 35 mm for a natural framing and 70 mm to isolate a group of cypresses or a farm in the landscape.

In the Val d'Orcia, around Pienza or San Quirico d'Orcia, the 24 mm can be useful when you want to include a road or a large expanse of hills, but it won't necessarily make the scene more impressive: distant elements will look small. Between 50 et 100 mm, you can on the contrary tighten the frame and visually bring the rows of hills closer together. With an APS-C body, check the equivalence: a 35 mm will frame like approximately 50 à 56 mm, so less wide. If you have to buy a lens for this trip, first look at what you photograph most often already; the light of dawn or late afternoon generally matters more than a few millimetres of focal length.