a great Bulgarian card I received last year
It shows Prohodna, a karst cave in north central Bulgaria, located in the Iskar Gorge near the village of Karlukovo. The cave is known for the two eye-like holes in its ceiling, known as the Eyes of God or Oknata. They have formed due to erosion and they let light pass through into the cave.
The cave is 262 metres long, which makes it the longest cave passage in Bulgaria. It has two entrances which lie opposite one another, known respectively as the Small Entrance and the Big Entrance.
Speaking of caves, I recently visited the most amazing one I've ever been to! hopefully will have the chance to write about it on the blog one day :)
there are two stamps on the card: the right one is from a set of 4 stamps issued in 2012, representing Regions of Bulgaria, the northwestern region in particular. The other stamp is from a set of 5 stamps issued in 1999, representing gold treasures of Panagjurište (a Bulgarian town and municipality)
thanks a lot to Tsvetana for this great card!