Thermen Maarssen is a large wellness resort on the Maarsseveense Plassen lake north of Utrecht with fifteen saunas and steam rooms, among them a 95°C fireplace sauna, a Banja sauna on the water with regular infusions, a panorama sauna with herbal infusions, a Himalayan salt cabin and a graduation sauna. A 5°C plunge pool cools you down. It is textile-free with no swimwear days, open daily 9:00 AM to 11:00 PM, from €50 a day or €40 after 4:00 PM.