Nestinarstvo, also known as Anastenaria, is a traditional fire-walking ritual observed in several villages in Bulgaria and Greece, particularly in the Strandzha Mountains and northern Greece. This ritual occurs every year from May 21 to 23, coinciding with the feast day of Saint Constantine and Saint Helen. The origins of the tradition can be traced back to ancient Dionysian cult practices, later integrated into Christian customs. During the celebration, villagers participate in a solemn procession to a small chapel, followed by a ritual bath in a holy spring and a symbolic meal of mutton. The highlight of the festival is the barefoot dancing on smoldering embers, where participants, known as nestinari, enter a trance-like state. While the ritual has become commercialized in tourist areas, the authentic experience can only be witnessed in six specific villages: Balgari, Brodilovo, Gramatikovo, Kondolovo, Kosti, and Silvarovo. In 2009, UNESCO recognized the ritual as part of the Intangible Cultural Heritage of Humanity.