Things to do
Thermal spas and hot springs
Steaming village squares, white terraces in the woods, and a free river spring near San Galgano.
Some of these places are hotels with treatments. Some are simply hot water coming out of the ground. I like both, at different speeds.
Bagno Vignoni
A tiny village whose square is a steaming sixteenth-century pool, fed by a spring used since Roman times. You look; you do not swim in the square.
Show on the mapPhoto: Spike, CC BY-SA 4.0, via Wikimedia Commons (cropped)
Bagni San Filippo
Warm springs under Monte Amiata, with white limestone terraces in the woods.
Show on the mapPhoto: LigaDue, CC BY-SA 4.0, via Wikimedia Commons
Saturnia and the Cascate del Mulino
A paid spa, and free falls at 37°C below the old mill. The falls get very busy, and they are not a wheelchair visit. The spa itself is the more accessible of the two.
Show on the mapPhoto: Markus Bernet, CC BY-SA 2.5, via Wikimedia Commons
Petriolo, near Monticiano, is a free sulphurous spring beside the river, and I have written a short piece about it. Montecatini Terme remains the straightforward spa-town stay if you want the train and a comfortable hotel. For places to sleep near the water, see Spa and thermal stays.
The Village Finder has a Spas filter under the map. A direct link to that filter is not available yet, so this opens the map and you can tap the filter there. Open the Village Finder