The Sinite Kamani Nature Park (Blue Cliffs) is located in the north if the city Sliven. The park is famous for its rock formations and covers an area of 115 square kilometres of the Karandila mountain. The Halkata (the Ring) represents a rock opening with the shape of an isosceles triangle with sloping base and top pointing at the sky. The fragile, about 10 metres high formation at the slopes of the Mt. Karandila, is located next to the lower Sliven - Karandila Chair Rope Line station.
The value 0.25 stamp shows the Halkata rock formation.
Тhe stamp of the miniaturesheet shows the old elm tree of Sliven
The elm tree is from the species Field Elm (Ulmus minor) and is about 1100 years old.
In the background is slightly visible the Karandila mountain with the TV tower on its top.