Never even heard of that. Does the kitchen have a second floor above it?

Bummer loosing the window in the kitchen.

A window frame with mirrors gives the illusion of a window. You will have a reflection of you when washing dishes, so smile :)

Found this photo of art behind a window frame.

How about a recessed lit area behind then stain glass behind sink.

This is an actual window, but with a mirror within the recess with led lighting around the whole square could be a beautiful accent. or keep as a pass thru & install stain glass

Or the common one,

Instead of a backlit window, glass cabinets with lights within & under cabinet lighting.

That will add storage as well.

Clear glass for displaying decorative items or frosted to hide more within.

Note: Having any glass or mirror will need more cleaning due to hot water steam.

So open shelving, but that too would need to be dusted.

Depending on the addition, a pass thru may be an option.

Kitchen pass thru with frosted glass doors

With some creativity & a good finishing contractor, the sink area can end up being just as beautiful of a focal point.

Hope that helps;)

Whatever you decide please post an after photo. It's nice to see the outcome & it helps others in the future who loose a kitchen window over sink, too.

Yes, unfortunately there is a second floor over the kitchen. If the window was left open to the addition, it would be looking into a hallway. I like the idea of the recessed lit area! I was even picturing putting plantation shutters on the window and putting a light behind it, but just don't know how to go about doing it. Thank you both for replying! I will definitely post pictures once I figure out what's going to be done.

I ate at a basement restaurant once. They had a window framed out, and at the back of the wall cavity they had a picture of the Italian countryside (it was a pizza place). They had concealed lighting (theirs I think was a linear tube, it being the 90s, but you could use LED undercabinet lighting) at the top of the "window," maybe recessed. It was psychologically effective, even if it wouldn't really fool anyone.