There are many thermal springs in Greece but the only ones in Cyclades can be found in Kythnos. The second name of Kythnos, Thermia, is derived from the word therma meaning thermal baths. The thermal springs are located in the village Loutra that owes its existence to the springs. Two hot springs can be found there Agioi Anargyroi, which is located indoors in the area of the spa and the outdoor spring of Kakavos at a distance of about 50m. The Agioi Anargyroi spring is saline, reaching 36 °C and is suitable for arthritis, rheumatism and spondyloarthritis problems. The source of Kakavos reaches 52 °C and its water contains bromide, iodide and sodium chloride, is ideal for skin disease and gynecological problems.
It appears that during antiquity, their use was unknown, although according to archaeological evidence, there was a sanctuary at the same site. Their use must have begun in Roman or Byzantine times, as archaeological findings in the area suggest. In 1782 at the spring of St Anargyroi were build a bathtub with roof and a changing room. Nevertheless, the locals showed little interest in the springs and surrounded them with beliefs about fairies and devils.
The first to understand the importance of hot springs were German doctors whom king Othon had brought to resolve queen Amalia's infertility problems. At the spa you can still see the bathtub they used. The building of the spa was completed in 1857.