Can you post a plan of how this fits in the house? Why can’t it just be a floor return?

Here is a larger copy of the floor plan. The area I am looking at is at the end of the foyer on left to the right of the elevator. This large return is necessary to put air back into the system. This is not an air supply vent. It is the only return we have for our house. If you only have one, it needs to be placed in a central location and this was the only place the a/c people could find that would work.

I really do not understand the whole thing and the plan does not show this and neither does the pic . Have a long talk with the HVAC person there has to be a better way.

I wish there was. You are correct; the plan does not show a return vent but every house must have one. Some homes have one in every room!

Can you wall the entire niche and turn the portion on the right into your coat closet?

I did find this on Pinterest. Similar to what I mentioned in original post. Decorative cover and then above the vent put a door for added storage. I would like to put a frameless door - something that just blends in with the wall because the foyer has so many doors already.

@Norwood Architects that was exactly what I mentioned to my husband. The electrician has already set up our internet access points in the existing coat closet and we were trying to avoid having to move them (added cost!). But I will definitely check with the electrician.

Same thing in my entrance hall- old house. It is 40” high and we drywalled it, put chair rail on sides so it blended with other walls and made a mahoghany tray top so it functions as table with decor.