Lake Vouliagmeni on the Athens Riviera is a lake fed by thermal springs among rock formations, run as a paid bathing and wellness venue with a restaurant. Its lakeside spa offers treatments and a 20-minute Lake Thermal Sauna Experience for 30 EUR, and is listed as open daily 10:00 to 19:00. Lake entry carries its own fee, summer hours are 08:00 to 20:00 from 1 May to 16 September, and same-day reservations are not possible.