What the word “Therme” on the sign actually tells you

The word costs nothing. Therme in German, terme in Italian, termál in Hungarian, thermal in half a dozen other languages — no authority grants any of them, no register lists who may use them, and nothing stops a leisure pool with a boiler from putting the word above its door. Compare that with Heilwasser or gyógyvíz, which are legal designations a state has to award. Therme is a mood.

So we counted what the word actually predicts, across 8,571 venues.

What the name predicts

561 venues carry a thermal word in their name. For 202 of them we hold at least one fact about the water — a pool or wellhead temperature, a named dominant mineral, a total mineralisation figure, a borehole depth, or an official medicinal designation. For 359 we hold nothing at all.

That last row is the one worth sitting with. A venue with no website and no data is simply undocumented — a pin on a map, and the internet has not caught up with it. But 165 of these places run a website, describe their saunas and their opening hours and their birthday packages on it, and say nothing whatsoever about the water they are named after. That is not an oversight. Water is the one thing a leisure pool cannot invent, and a page that stays quiet about it is usually quiet on purpose.

We are not calling those 359 fakes, and we do not list them as anything they are not. Some heat ordinary mains water and call the result a Therme, which is legal and common. Some sit on genuine thermal water and have simply never published a figure. From outside you cannot tell the two apart, which is precisely the problem with the word.

The name fails in the other direction too

If the word were a reliable label, at least the places that do have thermal water would use it. They don't. Of the 992 venues we classify as thermal baths, 499 carry the word and 493 do not — an almost even split. Hungary's gyógyfürdő and strandfürdő, Slovakia's kúpalisko, France's thermes in the plural and dozens of plain place names: a bath founded on a spring in 1870 has no reason to advertise in the vocabulary of a 2005 leisure development.

So the word neither confirms thermal water nor its absence. As a filter it is worth almost nothing, which is why this catalogue does not filter on it.

Where the word is fashionable

Germany leads by a distance, and German is also where the word has drifted furthest from its meaning: the -therme suffix has become the standard name for a municipal leisure pool with a sauna block, thermal water or no. Italy's 102 are mostly historic terme in the older sense. France's thermes are usually medical establishments attached to a spa town, where the water is regulated and the paperwork exists.

Our own category is not much better

Here is where an honest catalogue has to turn the lens around. Sixty-two of those 561 venues are filed in our database as something other than a thermal bath — a sauna, a hot spring, in one case a beach resort. It would be easy to present that as 62 places overreaching with their name. We looked, and it is mostly us.

Claudius Therme in Cologne appears twice. One record is a thermal bath with a pool at 35 °C and a Heilwasser designation, which its own website confirms in as many words. The other, under the operating company's legal name, is tagged as a sauna. That is not a venue exaggerating; that is one business mapped twice, once by its building and once by its sauna wing.

The second kind of noise is thinner still. Three separate venues in the catalogue are called simply Alpentherme — one in Gastein, one in Reutte, one with no town recorded at all — and the bare one cannot be told from its namesakes by anything we hold. A count that includes rows like that is measuring our own record-keeping.

Our categories come from OpenStreetMap tags, which describe what a mapper saw at an entrance. A large sauna wing gets tagged as a sauna. So treat the 62 as a to-do list of ours rather than a finding about anybody's marketing — and treat the category on any page here, ours included, as weaker evidence than the water figures beside it.

The two bugs behind this article

While assembling these counts we checked our own water facts and found a tenth of them wrong, twice over, in the same direction.

Sauna cabins posing as springs. Our extractor took the highest temperature it found near any word meaning spring or depth, and Quelle and Tiefe are ordinary German. So a sauna page qualified, and where a page carried both figures the cabin won. Seventeen of 169 wellhead temperatures were sauna heat — 95 °C, 90 °C — and the URLs admitted it plainly: one of them ended in /sauna-bochum-saunen-dampfbad. A round 100 °C turned up in six countries at once, including an Icelandic lagoon that bathes at 39, because boiling is how steam copy describes itself.

Pipes posing as boreholes. The same rule read any number followed by m as a well depth. A price list gave us a 5,000 m well. A municipal water-network page gave us 4,000 m, which was the length of the pipes. A sauna ticket page gave us 120 m. Forty of 167 depths came from pages that had nothing to do with water.

Both are fixed: a figure now has to stand beside a word that actually means what we are reading, and a page that mentions a sauna yields no wellhead temperature at all, even when a real one sits next to it. Losing a fact is the cheap failure. Printing 95 °C as a spring temperature is the expensive one, and it flatters the venue every single time — which is exactly why nobody would have complained.

How to settle it yourself in two minutes

1. Look for a number, not an adjective. A venue on thermal water publishes a temperature, and usually where it comes from. "Thermal experience world" is a description of a building.
2. Find the analysis page. Real thermal water has a composition, listed in milligrams per litre, with a sampling date. It is often buried two clicks deep under a heading like Unser Wasser or Analisi. Its absence on an otherwise detailed website is informative.
3. Check the legal term rather than the mood word. Heilwasser, gyógyvíz, água mineromedicinal are awarded by an authority. Therme, Wellness and Vitaltherme are chosen by a marketing department.
4. Distrust round numbers on the wrong page. A depth in a price list and a temperature on a sauna page are the two mistakes we made ourselves; a visitor reading quickly will make them too.
5. Ask the pool temperature separately. Water can arrive at 60 °C and still reach you at 34. The wellhead figure is geology; the pool figure is what you actually get into.

What we do with the ones that heat their water

We list them, under the name they use, and we do not pretend the water is something it isn't. If a venue heats mains water and calls itself a Therme, that is a real place with real pools and a sauna somebody enjoys — it is simply not a thermal bath, and the page will not claim otherwise. Where we hold a temperature, a mineral or a certificate, you will see it with its source. Where we hold nothing, you will see nothing, and now you know what that blank means: usually that the operator chose not to say.