This film takes us with the speleological expedition into the Karst regions around the city of Sofia in the heart of the Balkans where they visit seven caves they have never seen before. The journey begins in the beautiful National Park of Plitvice in Yugoslavia. Although this region is chieflly known for its lakes and high waterfalls, it is possible to find many caves there as well. There are two other caves about the 120 km north-east of the city: Saeva and Gradesnica, one of the most beautiful in the region. The journey contiues through the Vracanska plateau where there are many other unknown caves and deep chasms. In the end they visit the dangerous water system of Vreloto, and Duchla, the longest labyrinth cave in Bulgary.