Which cave system in Ukraine is the longest in Europe, with over 260 km of passages?

The Ukrainian cave system known as the longest in Europe, with more than 260 kilometres of mapped passages, is Optimistic Cave. Its current English transliteration is often given as Optymistychna Cave, while “Optimistic Cave” is an older English name for the same site.

The gypsum cave lies near the village of Korolivka in Ternopil Oblast, western Ukraine. It was discovered in 1966, and continuing speleological surveys have progressively extended the mapped network. Its winding passages, chambers and gypsum formations make it one of Europe’s major cave systems.

Optymistychna is also the world’s longest gypsum cave and is commonly ranked among the longest caves on Earth. Its passages are generally less like a single open tunnel than a complex maze shaped by the dissolution of soluble gypsum rock.

A common mix-up is Krubera Cave, also in the broader region and famous for extreme depth rather than length. Hölloch is associated with Switzerland, while Szczelina Chochołowska is not the European length record-holder.