The Romans were bathing fanatics—they built towns around mineral springs and constructed elaborate bathing halls. Water cures were also popular in the early 1900s, when thermal soaking was prescribed for arthritis, skin ailments and more. But medical advances after World War II made the spas seem passé. Today, with wellness a priority again (and disease and stress so closely linked), Europe’s classic baths are back in vogue.

Most of the thermal spas listed here are huge complexes of hot mineral pools, cold plunge pools, steam rooms and saunas. “Dress” codes vary: Swimsuits are sometimes optional, sometimes not. A two- or three-hour circuit of steaming, soaking and plunging is typical, with breaks in a “relaxing room” to replenish fluids by drinking mineral water or for a nap in a “relaxation chair” should the timeless ritual of taking the waters leave you drained.

ENGLAND
Thermae Bath Spa
Bath; thermaebathspa.com; day rate $108

The first spa in Bath was built by the Romans in A.D. 70. Today, history is represented by two 18th-century baths, the once-sacred Cross Bath and the Hot Bath, now reserved for Watsu massages. But a recent multi-million-dollar restoration has given Thermae Bath Spa a contemporary look. Its New Royal Bath, housed in a strikingly modern glass box, offers two thermal baths and four
aromatherapy steam rooms.

GERMANY
Baden-Baden
carasana.de; $23 for four hours at Caracalla, $43 for Friedrichsbad

The pure waters here haven’t changed much since Mark Twain visited in the 1880s: They’re still touted for heal-ing chronic inflammatory conditions like rheumatoid arthritis. Choose either the 32,000-square-foot Caracalla Spa (with a relaxation room and log-cabin saunas) or the neo-classical Friedrichsbad, where bathers follow a 17-step ritual, including a scrub-brush massage under a grand Beaux Arts dome.

CZECH REPUBLIC
Marienbad
marienbad.cz; day rate from $113

In its heyday, this spa town attracted 20,000 visitors a year—among them Goethe, Chopin and Thomas Edison. Today, the treatments range from spa-like (dry brush massage, peat wraps) to medical (acupuncture, EKGs). Guests are urged to imbibe large quantities of water from the spa’s six springs, each with its own mineral composition that provides different benefits. On-site doctors specialize in kidney and urinary-tract disorders, as well as infertility and sexual dysfunction.

AUSTRIA
Rogner Bad Blumau
Styria; blumau.com; day rate $54; double room with unlimited spa and two meals, $385

This spa/hotel looks like it was designed by Klimt. Curvy, multi-hued buildings sprout grass from their roofs; pools are connected by a swimmable tunnel and encircled by bridges. The spa’s Vulkania Lake draws 110-degree water from volcanic springs 9,300 feet underground. Rich in salt and minerals, the water helps speed up metabolism, boost circulation and firm skin. Massage, acupuncture and yoga are also available.

HUNGARY
Gellért Medicinal Bath Budapest; spasbudapest.com; day rate $18

The famous Gellért has nine medicinal pools, an indoor effervescent pool and an open-air wave pool, as well as five saunas and a solarium. The mineral waters here are used to treat everything from migraines to osteoporosis. You can also undergo an underwater “beam massage,” inhalation therapy or even dental treatment. With domed ceilings, marble pillars, bronze statues and mosaic floors, the Art Nouveau facilities (currently undergoing renovation) evoke the early 20th century when the spa was built.

SWITZERLAND
Engadin Bad Scuol
Scuol; scuol.ch; three hours from $22

The spa’s Roman-Irish bath combines bathing in steam with bathing in hot, dry air, an Irish tradition. Unlike elsewhere, you can reserve the facility for private use. The regular bathing area has a steamy outdoor pool with jets to pummel sore muscles while you take in the gorgeous views of the Dolomite mountains. The indoor pool is surrounded by relaxation chairs and jacuzzis; an outdoor Finnish sauna is heated to 203 degrees. The mineral-rich water does wonders for the digestive system.

ITALY
Adler Thermae
Tuscany; adler-thermae.com; day rate $160; double room with unlimited spa, from $315

The Adler, a classic bath at the lavish Hotel Adler Thermae, uses water from the ancient Bagno Vignoni springs—good for the bones, joints and skin. After a soak in the enormous, curving outdoor pool, you can make the rounds from an herbal-infused steam room to a Finnish sauna (made of olive-tree wood), to the Grotta del Filosofa, a steambath in a candlelit cave. The resident doctor will perform checkups, test for food allergies and treat you with herbal and floral remedies.