Consisting of 4 lakes. The lakes are former quarries that are filled with spring water over time. Quarries were used to extract quartz sand for the glass industry. The water of the lakes is very clean. It is never stagnant because underground sources constantly maintain the same water level. The bottom of each lake is covered by quartz sand. This sand differs from the usual in both properties and color, giving the water a bright blue color. Hence the name "blue lakes". The largest lake is the Big Lake (Velyke). It's depth is about 18 m and it's area is 20 hectares.