Đavolja Varoš (Devil's Town)

Đavolja Varoš ("Devil's Town") is a field of over 200 natural earth pyramids — tall, narrow pillars of rock and clay, many capped with a harder boulder that has protected the softer material beneath it from erosion — located in the Radan Mountains of southern Serbia. The formations stand between 2 and 15 metres tall and continue to be slowly reshaped by erosion, with some collapsing and new ones forming over time. The site was added to Serbia's tentative list for UNESCO World Heritage status and is sometimes cited among unofficial "wonders of the world" lists.

According to local Serbian Orthodox folk legend, the pillars are the petrified figures of wedding guests who attended a marriage between siblings — a union so sinful that God punished the entire wedding party by turning them to stone, with the bride's tears said to have created the two highly acidic, mineral-rich springs (Đavolja Voda and Crveno Vrelo, "Devil's Water" and "Red Spring") that flow nearby, both with a pH close to that of vinegar and conspicuously rust-red from dissolved iron and high arsenic content. Geologists attribute the formations to a combination of volcanic ash deposits, differential erosion by the area's unusually acidic groundwater (linked to long-extinct hydrothermal and volcanic activity), and the protective effect of resistant andesite boulders atop the softer pillars — a natural process that, notably, also explains the springs' striking colour and acidity that gave rise to the legend in the first place.