My instinct would be to hang the drapery panels close to the ceiling and add a simple, but substantial, valance that would come down just barely covering the upper window casing. Doing that would block the arched window, but it would be the best option if it's cohesiveness and symmetry that you're looking for. What are the ceiling heights in these rooms, how high up from the floor do the windows start and how tall are they (with and without the arch)?

Leave the very large arched window over the door open.

Can you show pictures of the windows from inside the main room with the arches?

The small arched windows above the main windows in the living area can be done several ways. Even though your arches aren't anywhere near this big you could still go over the tops with the rods. This is probably the best solution. You basically ignore the arches but hang the rods high enough so the drapes give height to the room and cover the arches if the sun is too bright at certain times. You might want to use sheers below the arches but either way would work.

I would mount above the arch, as a general rule of thumb it's better to go higher to elongate the room.

Contemporary Living Room · More Info

Sorry for the terrible lighting. Here's the window from the inside. Previous owners installed a valance and drilled the support bracket straight into the trim.