64 articles
Acqui Terme
Acqui Terme, Piedmont town on Roman Aquae Statiellae, famed for the 75°C Bollente sulphur-bromine-iodine spring, Roman baths, Nuove Terme and Regina spas, closed amid 2026 concession dispute.
Aponus
Aponus (Aponi fons) was the Venetic god of the Euganean hot springs near Padua, later identified with Apollo; his name survives in Abano Terme, and his sacred spring, the fons Aponi, drew healing pilgrims and Tiberius's golden dice.
Aquae Albulae (Italy)
Aquae Albulae (Acque Albule): sulphurous hypothermal springs near Tivoli, Rome, used since Roman times by Augustus and Hadrian, now the Terme di Roma spa with SSN-accredited cures.
Aquae Sinuessanae
Aquae Sinuessanae: sulphurous Roman thermal springs and baths of the colony of Sinuessa near Mondragone, Campania; cited by Livy, Strabo, and Pliny, visited by Narcissus, and still in therapeutic use today.
Badab-e Surt (باداب سورت)
Badab-e Surt (باداب سورت), also Badab Soort, is a stepped travertine terrace spring site at 1,841 m in Mazandaran, Iran, 95 km southeast of Sari, formed by two mineral springs, one salty and one iron-rich orange, registered as a national natural monument in 2008.
Bagnères-de-Luchon
Bagnères-de-Luchon (Luchon), Pyrenean spa town in Haute-Garonne, France, at 627 m near Spain; Roman-era thermal springs, revived by d'Étigny from 1759, Thermes Chambert 1857, Superbagnères ski resort, reopened 2025 rail line.
Bagni di Lucca
Bagni di Lucca is a town and spa center in Tuscany, Italy, known for thermal springs that made it one of Europe's most elegant 19th-century spas.
Banff Upper Hot Springs
Banff Upper Hot Springs is a Parks Canada-operated mineral pool on Sulphur Mountain in Banff National Park, Alberta, held at 37–40 °C. Canada's highest outdoor pool, first developed in 1886, with its 1932 heritage bathhouse restored in 1996.
Berkeley Springs (hot spring)
Berkeley Springs (Warm Springs, Bath) is a group of warm mineral springs, about 74°F, in Berkeley Springs State Park, Morgan County, West Virginia, famed since colonial times, visited by George Washington, with free public water and 1815 Roman Bath House.
Blue Lagoon (geothermal spa)
Blue Lagoon (Bláa lónið), geothermal spa on Iceland's Reykjanes Peninsula formed in 1976 from Svartsengi power plant effluent; silica-rich 37 °C seawater-freshwater mix, company founded 1992, repeatedly disrupted by eruptions since 2023.
Bormio
Bormio, an Alpine town in Alta Valtellina, province of Sondrio, Lombardy, Italy, famed for nine thermal springs feeding three spas (Bormio Terme, Bagni Vecchi, Bagni Nuovi), the 2,758 m Stelvio Pass road (1825), Giro d'Italia cycling, and World Cup skiing.
Bourbonne-les-Bains
Bourbonne-les-Bains is a commune and thermal spa town in the Haute-Marne department of the Grand Est region of northeastern France, built around hot springs exploited since antiquity.
Caldas Novas
Caldas Novas is a municipality in southern Goiás, Brazil, sitting over one of the world's largest non-volcanic thermal groundwater systems and drawing hundreds of thousands of tourists.
Calistoga, California
Calistoga is a small city at the northern end of Napa Valley, California, founded by Sam Brannan in 1859 and incorporated in 1886. Known for hot springs, mud baths, the Calistoga AVA wine region, and its hydrogen-battery emergency power system.
Cave and Basin National Historic Site
Cave and Basin National Historic Site, Banff National Park, Alberta: hot springs found by CPR workers in 1883, birthplace of Canada's national parks, designated a national historic site in 1981, home of the endangered Banff Springs snail.
Chico Hot Springs
Chico Hot Springs is a historic resort in Pray, Montana, Paradise Valley, founded 1900 as the Chico Warm Springs Hotel, with two geothermal pools (96°F and 103°F), a day spa, dining, and National Register listing.
Cold-water geyser
Cold-water geyser (soda pop geyser, CO2-driven geyser): a spring erupting cold water below 20 °C via exsolving carbon dioxide, not steam. Type example Crystal Geyser, Utah, created by a 1936 oil well; studied as analogs of CO2 sequestration leakage.
Desert Hot Springs, California
Desert Hot Springs, California: a Riverside County city in the northern Coachella Valley, incorporated 1963, famed for hot mineral spring spa resorts, the Desert Hot Springs Subbasin aquifer, and a 2026 data center moratorium.
Devils Hole
Devils Hole: water-filled geothermal cave in southern Nevada, disjunct unit of Death Valley National Park; sole home of the endangered Devils Hole pupfish, a 92°F pool with a 215-square-foot shelf and a half-million-year calcite climate record.
Dunton Hot Springs
Dunton Hot Springs is an all-inclusive luxury resort in a restored 1885 Colorado ghost town on the West Fork Dolores River, with 42°C calcium bicarbonate springs, 13-14 historic cabins, and no day-use access.
Ein Gedi (עין גדי)
Ein Gedi (עין גדי), a spring-fed oasis on the Dead Sea's western shore in the Judean Desert, a nature reserve since 1971 with four springs, ancient irrigation, a synagogue, and 2025 flood restoration.
El Tatio
El Tatio is a geyser field at about 4,300 m elevation in the Atacama Desert of northern Chile, one of the world's largest, with over 80 thermal features across 10 km2, studied geysers El Jefe and El Cobreloa, and community co-management since 2006.
Fly Geyser
Fly Geyser (Fly Ranch Geyser) is a small, constantly erupting geothermal geyser on private Fly Ranch in Washoe County, Nevada, about 20 miles north of Gerlach, created accidentally by a 1964 geothermal test well and now owned by the Burning Man Project.
Geothermal areas of Yellowstone
Geothermal areas of Yellowstone: about 120 thermal areas in Yellowstone National Park holding over 10,000 hot springs, geysers, mudpots, and fumaroles, including half of Earth's active geysers, heated by a magma chamber 5 to 10 miles below the surface.
Geyser eruptive mechanics
Geyser eruptive mechanics is the study of how geysers work: the subsurface reservoirs, constricted conduits, and boiling processes behind their periodic eruptions of water and steam.
Geyser types
Geyser types are the two classes of Earth's geysers: fountain geysers, which erupt from pools, and cone geysers, which erupt from mounds of siliceous sinter called geyserite.
Geysir
Geysir (Great Geysir) is the famous geyser of Haukadalur, South Iceland, whose name gave English the word "geyser"; first recorded in the 13th century, historically erupting up to 70 m, now mostly dormant beside the active Strokkur.
Grand Prismatic Spring
Grand Prismatic Spring, in Midway Geyser Basin, Yellowstone National Park, is the largest hot spring in the United States and third largest in the world, famed for rainbow thermophile color bands.
Hot spring
Hot spring: a spring discharging groundwater heated by hot rock, often volcanic. Also called onsen (温泉) in Japan. Key facts: Yellowstone's 10,000+ thermal features, 1948 onsen law, 1832 Hot Springs Reservation, hydrotherapy evidence.
Hot springs of Australia
The hot springs of Australia are more than 50 thermal springs and pools heated by geothermal groundwater rather than volcanism, many tied to the Great Artesian Basin.