Prohodna, one of Bulgaria’s most renowned caves, lies a mere 0.5 kilometers from the village of Karlukovo, epitomizing the Karlukovo Karst region. This geological marvel perches at an altitude of 250 meters above sea level, making it an accessible and traversable destination throughout the year. Intriguingly, a road runs directly above it, linking Karlukovo with Karlukovo Station, the National Cave House, the infrastructure of Bulgaria’s first geopark “Iskar – Panega,” and the town of Lukovit. Additionally, a fully renovated road from the village of Rumyantsevo, as well as from neighboring villages Petrevene and Belentsi, leads to Karlukovo.
A Tunnel Like No Other
Prohodna boasts the longest cave tunnel in Bulgaria, stretching an impressive 365 meters, with its vaults soaring to a height of 56 meters. The cave’s ceiling features a captivating phenomenon known as “Okna” (“The Chimneys”), often mistakenly referred to as “The Eyes of God” – two enormous, almost identically sized openings shaped like eyes. Whether viewed from below or from a height, these openings strikingly resemble eyes staring down at visitors. The awe-inspiring effect of light streaming through these apertures illuminates the cave’s interior, casting natural light on the bizarrely large formations, as the significant elevation difference between the two entrances allows daylight to primarily enter through the “Okna.”
A Geological and Historical Marvel
Prohodna is a cavernous corridor – a grand rock bridge oriented from east to west. It formed at the end of the Cretaceous period, some 66 – 68 million years ago. Historically, the waters of the Iskar River filled the cave, though now the river level sits below it. The active karst processes, seismic activity, and riverine actions characteristic of that era severed the cave’s karst corridor, leaving this segment isolated. Structurally, the cave consists predominantly of light beige to white robust, massive organogenic limestones. These limestones contain well-preserved fossils of shell detritus, bryozoans, bivalves, brachiopods, gastropods, sea urchins, and ammonites – more pronounced in the western part of the geological wonder. The thickness of the rock layers varies from 10 to 50 meters.
A Journey Through Time
Prohodna’s grandeur and unique features make it a symbol of natural beauty and geological history. Its accessibility, coupled with the fascinating interplay of light and rock formations, offers visitors an unforgettable experience, inviting them to ponder the mysteries of our planet’s ancient past.
