Prohodna is 262 metres (860 ft) long, which makes it the longest cave passage in Bulgaria. The cave has two entrances which lie opposite one another, known respectively as the Small Entrance and the Big Entrance. The former is 35 metres (115 ft) high and the latter reaches 42.5 or 45 metres (139 or 148 ft)[2] in height. The cave owes its name, which literally means The Eyes of God -Thoroughfare Cave or Passage Cave.The size of the Big Entrance of Prohodna makes it suitable for bungee jumping, and it is among the popular spots in Bulgaria for that activity.

Пещерата Проходна е най-дългият пещерен тунел в България, с дължина от 365 метра и с височина на сводовете си от 56 метра.[2] В тавана се е образувал феноменът „О̀кната“ („Очите на Бога“, „Комините“) – два огромни, почти еднакви по големина отвора с формата на очи.