There's planty of nice day hikes...in which area are you staying?
if you like mountain hikes you can go in Pistoia Area, to Abetone and nearby.
if you like countryside hiking you can visit Carmignano area (near Florence) or Siena Area (especially south of siena)
if you like seaside hikes you can visit Maremma Area (south of Tuscany)
Please, don't hesitate to contact me if you need any further stuggestion
Enjoy your holiday
http://www.villacastelletti.it about 7 years ago