Prohodna (Vhod) in Lukovit

You're standing at Prohodna, a cave in the Iskar Gorge, close to the little village of Karlukovo in northern Bulgaria. Take a look at that huge opening in the rock. It's one of two entrances, and they face each other from opposite ends. So you can quite literally walk straight through the hill. That's where the name comes from: Prohodna means something like passage cave.