An ovoo is a traditional monument originally linked to the cult of mountains and sky. It generally takes the shape of a pile of stones and is located on top of hills and mountains, or any other high place. In the regions where stones are too few, the ovoo can be built with sand, soil, or branches. Although many ovoos are just built as distance markers on the passes of mountains most of them are considered as sacred monuments.
A Mongolian must never pass outside an ovoo without stopping. He must dismount, make an offering to the ovoo (putting money on it, cutting some strands from the horse's tail and tying them to the ovoo, or pouring a bit of vodka or milk on it), and add a stone on the ovoo. The ovoo plays an important role in the sacrifice ceremonies.
The cult of ovoo is generally held at the end of summer. During the veneration, three branches are placed on the ovoo and some flags made with fabric or paper and covered with religious texts are tied to it. Nearby or on the ovoo, believers burn juniper by way of incense on a three-stone row leading to each side of the ovoo. Nearby or on the ovoo, a fire is lit and believers make offerings of meat, dairy products, vodka or airag.
Then a shaman executes an expressive dance or lamas read, while believers sit northwest the ovoo. Nowadays, the growing involvement of lamas in the benediction of ovoos made the involvement of shamans greatly decrease. Once the ceremony achieved, believers share the remaining meat and dairy products, leaving a piece for the ovoo. The Naadam Festival has been giving rise to a ceremony of veneration of ovoo for a long time.