Oboos were always constructed on the tops of hills. Usually the tallest hill was selected for the site of an oboo, but a smaller hill that was the location of a great military victory could also be selected.
Oboos varied in their appearance. A simple stack of stones could serve as an oboo, or carefully selected stones could be arranged into a specific pattern to represent an oboo. The vast majority of stones used for oboos were not marred with hand carvings or drawings.
The presence of an oboo transformed a hill into a holy site, used by shamans and lamas of the nomads of the steppe. Sites with oboos were used for special ceremonies or to cast communal spells. An oboo increased the power of these spells.
Since oboos were sacred sites, even an oboo used by a sworn enemy was usually left alone because the nomads feared risking the wrath of the gods.