Fact 1012 — Optymistychna and Ozerna Caves

Optymistychna in Podillia is Ukraine’s longest known cave and the world’s longest gypsum cave. The Encyclopedia of Modern Ukraine reports more than 260 km of explored passages, while Ukraine’s speleological cave catalogue lists a lower figure of about 216 km, reflecting different dates and surveying records. Nearby Ozerna is another major gypsum cave; the catalogue lists about 144 km for it.