I'd run a dual curtain rod across the entire window wall with sheers and a blue pattern that matches the wall color. That way you could have sheers or nothing but the curtains would frame the window.

I would recommend a Flat Roman shade in a contemporary pattern, to play off the art above the fireplace. Working with the grey tones in the space already.

Or perhaps do a wall of grey drapery, bold and dramatic, floor to ceiling like this!

I like both of Gordon's Window Decor's ideas. I think I'd do both -- roman shades -- or natural shades -- AND a curtain. Something substantial. I've been really happy with the velvet curtains I bought at Country Curtains. Grey might be nice -- also maybe burgundy or even an emerald green? Looks like a great space.

Definitely flat roman shade. Your window has a very beautiful trim, you don't want to cover it.

This room below has Mid century vibe:

Logan Circle Residence · More Info

A neutral color shade that may work too:

The room below has similar color as yours

Historic Victorian Bedroom · More Info