Complex sentence: Charles is depicted as a chivalrous knight and sovereign riding a large, muscular white horse--possibly a Lipizzaner--under a neoclassical triumphal arch, from which is hangs a drape green silk.
Split into simpler sentences: Charles is depicted as a chivalrous knight and sovereign. He rides a large and heavily muscled white horse-possibly a Lipizzaner-under a neoclassical triumphal arch, from which fall hangings of green silk.