Lake Hévíz Thermal Lake

Geothermal & TravertinesZala,Hungary

Western Hungary's thermal lake, the largest on Earth you can swim in, renewed every three and a half days by a spring 38 metres down.

September·Peaking now

Jun–Oct

Regulars drift among the lily pads in rented rubber rings — high summer is the lake at its most social.

Year-round The spring holds the lake at 23-35°C every day of the year; only the steam and the lilies come and go.

Lake Hévíz never gets cold. Warm water rises from a spring cave 38 metres below the surface and pours out fast enough to replace the whole lake, some four and a half hectares of it, every three and a half days. The hotter of its two vents runs at about 41°C, so the surface holds 33-35°C through summer and rarely drops below 23°C even when the air is freezing. Larger thermal lakes exist, but this is the biggest one on the planet you can actually get into. Out in the middle you are out of your depth, so the regulars do not swim at all. They hang in rented rubber rings and drift among the lily pads, heads out, talking. The lilies are the other surprise: Indian water lilies flowering from June into late autumn, in water warm enough to carry them through a Hungarian winter. In December the lake steams into the freezing air and you swim inside a white fog. Under the swimmers lies a peat bed eight metres thick, and its black mud is still prescribed for worn joints at the rheumatology hospital on the shore. Count György Festetics put the first bath house out over the water in 1795, and the town's name is simply the old Hungarian for hot water. The lake is open every day of the year, but its landmark is not. The bath house standing on piles over the water has been shut since spring 2025, after gas seeping from the lake bed damaged the pile heads and the structure began to shift. You enter from the shore now and bathe outdoors, and a replacement is due to be built from 2028.

Worth knowing

Good to know

The lilies are open in the morning and shut by midday — each bloom lasts about three days and closes in the heat, so come early if you want flowers rather than pads.
This water is dosed, not soaked in — it is sulphurous and mildly radon-bearing, tickets are sold by the hour, and anyone with a heart condition or an overactive thyroid should ask a doctor first.
In winter the water is the easy part — the walk to the steps in freezing air is not, so bring slippers, keep your head dry, and leave a robe at the rail.

Things to do

1
Swim in the steam on a freezing morning
When the air goes below zero the lake gives off dense steam, and the far bank, the bare trees and the turret of the old bath house come and go inside it. You are warm to the shoulders and cold on the scalp, and the sound carries strangely — this is the day Hévíz looks like nowhere else in Europe.
2
Drift through the water lilies
Great rafts of lily pads cover much of the open water from summer into late autumn, and you can float right up to them. Get there in the morning while the flowers are still open — they close as the day warms — and you are swimming among tropical plants that have survived here since 1898.
3
Take the cure the way the regulars do
Almost nobody here swims lengths. You collect a rubber ring, work your way out over water too deep to stand in, and then just hang there and drift with everyone else, an hour at a time. It looks odd for the first five minutes. Then the warm water takes the weight off your joints, and you understand why people book a fortnight of it.
4
Drift out to the old bath house on its timber piles, while it still stands
From your ring, work your way toward the long timber buildings that stand over the lake on their larch piles and follow the run of walkways above the lily pads. The central bath house has been shut since 2025 and is due to be pulled down and rebuilt from 2028, so drift close and take it in while it is still there.

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Nearby

242 km