The illuminated, 20km-long karst cave at Postojna

Millions of years in the making, Slovenia's limestone underworld is one of the country's top attractions.

A subterranean network of caves lurks beneath the landlocked terrain southwest of the Ljubljana.

Spending the night in a converted military prison is not half as grim as it sounds. Sure, there's shared toilets, strict rules about noise and smoking, and rows of barred cells behind which inmates once languished.