Bulgarian speleologists have discovered a new gallery in the Optymistychna Cave in western Ukraine, enough to help it reclaim the second spot in the list of the world's longest caves, private broadcaster bTV reported on May 13.

The newly discovered gallery was called Bulgaria, bTV said.

The Bulgarian expedition, which included nine speleologists, arrived in Ukraine on April 25 and spent seven days underground together with local colleagues, researching the cave and discovering 50km of previously unmapped terrain.

Added to the current 220km, Optymistychna, also known as Optimisticeskaja after the Russian spelling of its name, is now more than 270km long, taking the distinction of the world second longest cave from the Jewel Cave in South Dakota. Only the Mammoth Cave in Kentucky is bigger.

“Together with our Russian colleagues we were prepared to work at least during several expeditions to discover some new parts of the cave,” Martin Taranteev, head of the Bulgarian expedition, told bTV. “We did not presume that it could be found so fast and so easily,” he said.

The new discovery was made on the day of the Othodox Easter, April 27. This is one of the biggest discoveries for Bulgarian speleology, bTV reported.

The cave, comprising a dense network of galleries on several levels, was first explored in 1965.