Complex sentence: In architecture the frieze is the vertical part of an entablature, whether plain or decorated with bas-reliefs, that lies upon the architrave ('main beam') and is capped by the moldings of the cornice.
Split into simpler sentences: In architecture the frieze is the vertical part of an entablature, whether plain or decorated with bas-reliefs. It lies upon the architrave ('main beam') and is capped by the moldings of the cornice.