For our Geo Quiz today we're searching for a country that's a caver's delight. The mountains along this country's Adriatic coast are full of sinkholes, deep caverns, and underground streams.

A view of Mt. Velebit

Some of the world's deepest and steepest caves are found here. There are at least 3 caves that extend down more than half a mile. One of those caves, Velebita, also has another claim to fame:

"That cave has the biggest vertical, underground drop in the world, that drop is one piece, single drop. 1683 feet." (Darko Bakšic)

So what central-south European country is home to this extraordinary subterranean chamber?