Natural Park Sinite kamani (eng: The Blue Stones) is considered one of the most attractive parts of Eastern Stara Planina. And for a very good reason. With a total area of ​​11380,3 ha, the Park is an unparalleled blend of peculiar but fascinating rock formations, impressive caves and waterfalls, unique flora and fauna. The numerous archaeological monuments and historical sites here attest to the infinite impact of the hills on the life and spirituality of the people that settled and inhabited the place in ancient times.

The blue color of the stones, hence the name of the Park, can be observed only under specific conditions (most often at night) and results from their geological composition and content of quartz-porphyry (a type of volcanic rock containing large porphyritic crystals of quartz).

Nature Park "Sinite kamani" takes pride in its astonishing biodiversity - there are over 1,000 plant species, including many rare and protected species. The fauna is represented by 244 species of vertebrates and 1153 invertebrates. Parts of its territory fall within a broad bird migratory route -the Via Pontica Flyway. Protected birds of prey, incl. Griffon Vulture (Gyps fulvus), and their rocky habitats are of special interest to ornithologists.

Among the most famous landmarks in the "Blue Stones" is the rock phenomenon “Halkata”(eng: The Ring) - a symbol of the town. The rock formation stands among stone cliffs and inaccessible crags, 550 m. above the lower lift station. Local legends have it that once the "Ring" was "amid the sea" and ships used to be anchored to it. Young couples also believe that if they go through the "Ring”, they will remain together forever. The other fascinating rock formations are quite appealing, as well: Rakavichkata, Kuklite, Iglite, Kalojanovi kuli, Bachvata, Enyova bulka, Ovcharya, Skalata na smartonosnoto nakazanie, Skalata na placha, Kamilata i Zhabata, the caves Zmeevi dupki, Futula, Hajdushka, Peschanik , to name but a few.(respectively in eng: The glove, The dolls, The needles, The towers of Kaloyan, The barrels, Enyo’s bride, the Shepherd, the Rock of death penalty, The Rock of tears, The Camel and The frog, The holes of the Dragon, Fitula, Haidut cave, Peschanik).

Sinite kamani Nature park includes various historical sites from different periods: Antiquity, the recent past, the National liberation( i.e. Thracian sanctuary, Roman fortress in Hisarlaka, etc.). During the Late Middle Ages, the so called Sliven’s Little Mount Athos was situated along Manastirska River, and one can still see remnants of the old monasteries.

Many ecotrails and various thematic hiking trails mark the territory of the Park. The chairlift connects "Sinite kamani" Visitor Center with the famous area of Karandila.

The natural resources of the park provide excellent conditions for practicing various forms of specialized tourism - mountaineering, caving, biking, delta and paragliding, trekking and others.