Tuscany is well known for its thermal baths. The volcanic activity in the area gives rise to many sulphur-rich hot springs. The Maremma also features a number of them. Please note that in Italy thermal baths have a long medical tradition, so don't be surprised to find a wide range of wellness treatments on offer.
Terme di Saturnia Spa & Golf Resort
Argentario Golf Resort and Spa
Not a thermal bath in the true sense, but a wellness centre on the coast.
Parco Regionale della Maremma. This nature reserve offers a number of splendid walking trails, unspoilt beaches, as well as the possibility of excursions by bike, horse or canoe.
Trekking Roccastrada is a hiking route of 146 km through the hills on the border of the provinces of Grosseto and Siena, that can be walked in 8 stages. The route is described in English in this pdf-document.
Touristic biking routes are detailed on the website of PisteCiclabili.com in Italian only!.