Hola Weiping

Thanks for alerting us on this. We checked the text and there was actually a mistake in how that part was narrated. There was a "aunque" clause that needed a main clause to make sense. That part has been re-written (and this new text will be re-imported soon, but it will take a few days to show correctly in the site). The correct text will be:

"Deberíamos subrayar que la ventana y el balcón aparecen como referentes temáticos a lo largo de toda la historia del arte, desde el Renacimiento hasta nuestros días, pasando por el Barroco y el Romanticismo. En este último, deberíamos destacar la obra"Mujer en la ventana" de Caspar David Friedrich, aunque tal vez sean más cercanos a la cultura española los ejemplos de Dalí y su "Muchacha en la ventana"o "Mujer sentada ante una ventana" de Picasso."

Does that make sense now? 

What the author is explaining here in this paragrapgh is that we need to consider that that theme (windows and balconies) has actually been a theme in the past, it's not new, and it gives some examples. 

Let us know if there is still something to clarify.

Saludos cordiales

Inma