some scholars postulate that the russians borrowed onion domes from muslim countries - possibly from the khanate of kazan, whose conquest in 1552 ivan the terrible commemorated by erecting st. basil's cathedral. eight of the nine domes featured on st. basil's cathedral represent each attack on kazan. the ninth dome was constructed 36 years after the siege of kazan as a tomb for ivan. the ornate finishes of these domes are bright in color and bold in shape as they are adorned with pyramids and stripes, and many other patterns seen on other cathedrals than basil's. some scholars believe that onion domes first appeared in russian wooden architecture above tent-like churches. according to this theory, onion domes were strictly utilitarian, as they prevented snow from piling on the roof.