Spas with thermal pool

Florence, Tuscany

Hotel spa inside the Helvetia & Bristol in central Florence, with two heated pools, a calidarium, sudatorium and tepidarium, open daily to walk-ins and hotel

Scottsdale, Arizona

Hotel spa at the Inn at Eagle Mountain in Fountain Hills with sauna, steam room, pools and a $69 60-minute massage as its signature treatment.

Hunter Valley, New South Wales

Large day spa at Chateau Elan in Hunter Valley with 17 treatment rooms, a float tank, outdoor mineral spas and couples' treatments; day passes and walk-ins

Calistoga, California

A 20-treatment hotel day spa in Santa Rosa with an indoor caldarium plunge pool, eucalyptus steam rooms, and walk-in or reserved day passes for adults 18+.