Historical sacred natural sites are natural sites associated with sacrifice, worship, healing, prayer or other religious or ritual activities according to folkloric, archaeological, historical, ethnological or other data.
Hiis, usually translated into English as sacred grove, is mostly a specific place that is called “hiis”. It can be a tree, grove, forest, stone, spring or landscape. The word “hiis” in its various dialectic forms has been used to describe the place, its sacredness and/or nature spirits that are believed to dwell there. “Hiis” as a place name is more characteristic to North Estonia; South Estonian people call their sacred places rather just sacred (sacred tree, sacred stone etc).
Throughout medieval and modern times, holy places were mentioned only in connection with the descriptions of the local people who worshipped idols. Such texts only mention the holy sites and the fact that offerings were made there, reflecting mostly the veneration of trees, but also of stones, and other objects (see Sild 1937). In such descriptions trees have been considered the most important elements, which is also referred to by Latin (lucus sanctus, Folklore 42 25 Hiis Sites in the Research History of Estonian Sacred Places sancta silva) or German (heilige Hain) terms.
“And before Christianisation heathen Livonians held terrible rituals of superstition with the sun, the moon and the stars, also with snakes and other animals. They also considered some groves sacred, where no trees could be cut. And they believed that whoever cuts a tree or bush in this sanctuary would die. (Russow 1967: 20)”
“They do their devotions commonly upon hills, or neer a tree they make choice of to that purpose, and in which they make several incisions,” they cut all branches of trunk up to the top, “bind them up with some red stuff, and there say their prayers, wherein they desire only temporal blessings” (Olearius 1669: 33).
The word hiis appears also in the first Estonian Bible translation in 1739, where it has been used to translate the Hebraic word ashera, which stands for a fertility goddess, her idol, and her cult place (see more Koski 1967: 44–46). Hiis has been used to signify pagan cult buildings. As the word has been employed to refer either to a place or a person, Mauno Koski suggests that in the 18th century hiis in Estonian and Finnish could have meant both – a hiis site and the mythological beings living there (Koski 1990: 417).