In the beginning of April researches at spring Vrelo will be continued on Balkan mountain. It is assumed that spring comes out from huge underground lake which is still unexplored and considered to be a great mystery. Here occurs one strange phenomenon each year at almost the same time, the spring dries up for few hours at religious holyday Preobraženje.

Last year German divers who were exploring this lake, managed to dive 48m deep, but due to strong flows at this depth they gave up and this year they are returning with adequate gear to continue exploration beyond this point. They are hoping to finish task this year and to manage fully exploration of the Vrelo.

Spring Vrelo is another unique characteristic of Balkan mountain and proof of its intact nature.

Source: http://www.staraplanina-babinzub.info/sta-krije-podzemno-jezero-na-staroj-planini/