Complex sentence: During the procession, the street lights of the city are turned off and replaced with pitch torches; the only electric lights to be seen are those of Christmas trees shone through the windows of private households.
Split into simpler sentences: During the procession, the street lights of the city are turned off and replaced by pitch torches. During this time, the only electric lights to be seen are those of Christmas trees, which can be seen through the windows of private households.