Demir Baba ("Iron Father") is venerated as a 16th-century Alevi-Bektashi saint and healer. His heptagonal sandstone mausoleum, with a rectangular antechamber and a hemispherical dome, was built atop a likely ancient Thracian sacred site within the Sboryanovo reserve near Sveshtari, Razgrad Province. A cult complex with a holy spring grew around the türbe, which remains an active Alevi pilgrimage site and one of Bulgaria's 100 National Tourist Sites. (Sources: Wikipedia 'Demir Baba Teke'; Lyubomir Mikov, Cult Architecture and Art of Heterodox Muslims in Bulgaria 16th–20th c., Sofia 2007; Wikidata Q723505.)