Complex sentence: There were the hills sloping to the beautiful lake, the lake itself, of similar size and form to Onondaga Lake, and salt springs and had springs of salt and fresh water mingling together.
Split into simpler sentences: There were the hills sloping to the beautiful lake, the lake itself, of similar size and form to Onondaga Lake, and salt springs. They were both about the same size, had springs of salt and fresh water mingling together.