Kristall Wohlfühltherme Ludwigsfelde

The Kristall Wohlfühltherme sits on the Ostverbinder ring road in Ludwigsfelde, roughly half an hour south of Berlin, and belongs to the Kristall Bäder group, whose house style of gemstone-themed sauna cabins is applied here in full. Bathing is in brine rather than plain water: the operator states that its four indoor and two outdoor basins are all fed with medicinal thermal brine enriched with minerals or with sodium bicarbonate, and that water temperatures across the complex run from 28 to 36 degrees. The indoor line-up covers a 36-degree brine pool at 3 to 5 per cent salinity, a 36-degree bicarbonate pool developed specifically for the group, a 28-degree fresh-water basin for contrast, and a milder 33-degree brine pool under a large glazed roof with direct access to the open air. Inside the latter is a grotto modelled on the Blue Grotto of Capri, lit so that the water reflections carry onto the rock.

Outside, the headline basin is a natural medicinal brine pool at about 12 per cent salt and 36 degrees, strong enough for the buoyancy to resemble the Dead Sea; a gentler 33-degree brine pool, a current channel that is illuminated after dark, and a whirlpool complete the open-air area, with a cold plunge at around 11 degrees for use between sauna rounds. The operator counts some hundred massage jets set into the walls and floors of the basins. Steam rooms are treated as bathing highlights rather than saunas: a 45-degree mist cave, a 48-degree brine cave with salt-laden air, and an Ottoman hamam with a heated marble slab.

The sauna offer is unusually large for a bath of this size. Eight themed cabins are indoors, graded from a 100-degree professionals' sauna down through crystal, amethyst, lemon, rose quartz and Hildegard von Bingen rooms to a mild 60-degree rose and lavender cabin, plus a colour-therapy saunarium at 70 degrees. Five more stand in the garden, installed inside dismantled alpine herdsmen's huts, mills and grain stores that the operator dates at up to almost 300 years old; among them are a coffee sauna, a Russian-style banja lined in birch with whisk infusions, and the newer Kristall Palast show sauna, faced with around 30 tonnes of marble and run between 70 and 100 degrees depending on the performance.

A separate sports hall holds 25-metre lanes at 26 to 27 degrees with spectator seating, opens at 07:00 on Tuesdays and Fridays for early swimming, and can be opened along one side in summer onto a lawn; a parent-and-child pool at 33 degrees adjoins it. Free aqua Zumba sessions run four times a day from Friday to Sunday in the gentle-brine pool. The therme is open 09:00 to 22:00 Sunday to Thursday and to 23:00 on Fridays and Saturdays, closed on 24 December.