The Geomunoreum lava tube system in Jeju Island's Manjanggul Cave is more than 13 kilometers long, but just one kilometer is open to the public. Tubes like this are formed when molten lava underground starts to solidify, creating long caves that snake under the earth's surface.

Manjanggul Cave is packed with geological treasures, including a 7.8 meter high lava column – the world's tallest. While stalactites are formed when the ceiling of the tunnel melts, lava columns are created when the molten liquid itself drips through a hole in the cave's ceiling.

The lava tube is just one of the island's natural wonders. Jeju is home to the Hallasan volcano, South Korea's highest mountain, and has been listed as a UNESCO World Heritage Site for its unique ecology.

Its warm climate has long made Jeju a top holiday destination for South Koreans, who have dubbed it "honeymoon island" for its popularity among newlyweds. 

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