The exhibition Magic of the Mask, which was put up at the National Ethnographic Museum, showed costumes and masks of Kukeri (mummers) from different regions of the country. Although the traditions Kukeri and Sourvakari are present in many parts of Bulgaria, they are the most vivid and colorful in western Bulgaria.

In the period from Christmas to New Year, also called Sourva, the Sourvakar games and rituals, typical of Western Bulgaria and the region of Sredna Gora, are performed. Masked men dance on the first day of the New Year, January 1, in some places this ritual is performed on January 14, which was New Year's Day according to the old calendar.

From ancient times there has been a belief in Bulgaria that in the period from Christmas (December 25) to Epiphany (January 6) the skies are open and Heaven and Hell merge. These days are also known as the Twelve Dirty Days. It is believed that during this “impure” period, evil spirits and creatures from hell are roaming amongst the people, doing ill things to them and spreading disease. The Dirty Days end with the blessing of the water on the Epiphany, Saint Jordan's Day when, people believe, the cosmic and social order is restored and the old year gives way to the new.

In this period, following the long-established traditions, groups of masked men and lads roam in the villages of Southwestern Bulgaria. They are generally called Sourvakari, but some local variations are also known – Babugeri, Djamali and Startsi. The masks, worn by the dancers in the Sourva ritual, are typically made of wooden structures, decorated with sheep and goat furs, wings and feathers, horns, pieces of cloth, corn leaves and hemp. Some of the masks have two faces. The wearers of these masks believe that the two-faced mask has greater protective power, because it also shields their back from powers of impure nature. The men also have huge bells, tied to their belts; some of them would thrust an old revolver in their waist-belt and others would throw on their backs bunches of yarn-beam, tightly fastened together with a rope, which stand for guns.

A few days before Sourva, each of the groups of dancers votes to elect its leader – Byulyukbashiya – a most respected and honorable man in the village. Some of the most typical dancing personages are: Bride, Groom, Priest, Bear and Bear-ward and Color-bearer. The role of the Bride is usually played by a young man, disguised as a bride. The Bride is accompanied by the Groom and the Color-bearer. The Priest is dressed in a cassock and a kamelaukion, carrying a tin can instead of a church-lamp, in which is burning not some kind of divine incense, but a dried hot pepper. The Bear and the Bear-ward pretend to tramp over the hosts' back, thus bringing them good health.

The group roams through the whole village, entering each and every house and chasing the evil spirits away with their fearful masks and costumes and the loud sound of their bells; an occasional gunshot may also be heard, as a contribution to the general clamor.

The Sourvakari dancers bless the house-owner and his entire family and farmland and living-stock and all of his belongings, wishing them a lot of health and fertility throughout the New Year; the hosts treat the dancers to various dishes and usually give them small presents.

In some regions of the country this ritual is performed till April.