Sehusa Wasserwelt

Sehusa Wasserwelt stands at Engelader Straße 3 in Seesen, on the northern edge of the Harz, and is run by Wirtschaftsbetriebe Stadt Seesen/Harz GmbH. The water here is genuine brine, not branding: the operator states that its brine pool is filled with "einer natürlichen, dreiprozentigen Thermalsole" at 32 °C and describes it as soothing for rheumatic complaints. The house gives its total water volume as 835,000 litres.

Alongside the brine area the hall holds a 25-metre swimming lane, a 3-metre diving platform, a whirlpool and a massaging waterfall next to the brine pool, a non-swimmers' pool at 29.5 °C with a pirate ship for children, and a toddler area with coloured water toys. The slide is the Crazy Cone, a 75-metre tube slide with LED light effects that drops from 6.60 metres through an oval tube into a sideways funnel, the cone, and can be ridden in a two-person tube. Parts of the swimmers' pool, the children's pool and the brine pools are reserved for courses, schools and clubs at times during the week.

The sauna landscape has five heat rooms: a Bi-O-Bad moist warm-air bath of solid timber at 50–60 °C with 30–40 % humidity and herbal infusions, a Finnish sauna at 90–100 °C with about 10 % humidity, built in 2001 from solid softwood logs, a rustic log-house sauna at about 90 °C in the sauna garden, a Maa-Sauna built of 25 to 30 cm pine trunks over a stone-lined pit, with a permanently burning stone stove and temperatures up to 120 °C, and a steam bath at about 45 °C with roughly 100 % humidity. A generous sauna garden with an outdoor pool, loungers and lawn adjoins them, and there is a quiet room and a colour-light therapy installation.

The bath opens Monday to Friday 10:00–21:00, with an early-swimmer session on Thursdays from 06:00 to 10:00, and Saturdays, Sundays and public holidays 10:00–20:00. The sauna opens Monday to Friday 14:00–21:00, Tuesdays for women only, and 10:00–20:00 at weekends and on public holidays; bath and sauna must be left 30 minutes before closing. The whole house closes at Easter, on Ascension Day, for an annual maintenance shutdown in June, and on 24, 25, 26 and 31 December 2026.