Unless you can think of a reason you need then? It's spelled.........D R Y W A L L. They look like mistakes. : )

Frame, drywall, replace base molding, paint. Hang art.

You don’t want the first thing a guest sees to be your shoes! If you need a place for shoes, add the shelves but have a custom door made for the nook to hide them. Do you have a closet for guests’ coats? The deeper nook could have a couple of coat hooks added for coats.
You could put shelves for books or showcase a narrow sculpture or a skinny vase with dried branches and seed pods.
It’s hard to figure out what a builder was thinking of when they leave odd little spaces like that.

Guests or me - I don't want to look at shoes in my front entry. Can you get rid of part of that wall and make a closet?

I like the shelves for shoes or coat rack idea for guest visiting for a couple of hours. I don’t wear shoes or let guest wears shoes in my house so that is a great place to store shoes.

Our shoes are stored in the front entry because we don’t wear them in the house. So of course the front entry is a logical place for shoe storage. IKEA has many shoe storage options but since you have these odd spaces what I would do is take measurements then go to The Container Store and have them set you up with the proper storage for inside these odd spaces, like, pull-out bins. Then you only have to find out how to provide a door. The easiest way would be to purchase tension curtain rods (and yes they come in pretty small sizes) and sew a curtain with a rod pocket in the top and bottom out of a beautiful fabric. hang it from the top of the opening - the very top - and weight the bottom hem with pennies or curtain weights. The larger nook could be very handy for storing other things as there is very little storage available in condos.

Wow builders are so creative these days at designing ridiculous spaces! Whatever happened to basic floor plans? Hope you can turn these odd spaces into beautiful storage. You won’t need much fabric, so get something really beautiful, you will probably need three yards (your ceiling height plus a foot) and can cut it down the length to provide the two curtains. Check out Marimekko online.

It depends on if any are a support wall, but I would have a contractor look at it and see if they could be combined into one closet.

You own the condo, right? So the walls are yours to tear out and rearrange, if you want to do that.....assuming there is no landlord or condo association that must approve or deny your desired changes. With walls made with drywall, you have to realize that it is just a surface covering, and underneath the drywall skin is the real structure of the wall, the bones if you like, which are the wood studs, along with whatever wiring, pipes for water/gas/sewage, ventilation ducts (etc) might be running through the walls like blood vessels.... You can make better decisions about what to do with the space if you understand what's behind the drywall; I'd do some investigating to try and find that out. It would be great if the condo management has the construction plans for you to check.

I suspect that the niches cannot be combined, probably because of piping in the walls.

Have something built...suggest the 4th photo down on the left side...rotates to mirror.

https://visualhunt.com/tall-narrow-shoe-rack

Thanks all! I am leaning towards installing some type of shelving and hanging a chic curtain over it... or maybe getting a Container Store/Closet company's thoughts on it too. I'll take storage wherever I can get it!

If they had never existed, would you add a similar thing? No? then you have your answer and don't NEED THEM. The are someone else's kludgy design mistake. Obliterate with drywall.

I agree 100% with Jan-this is a design flaw-frame, drywall, replace base molding, paint. Hang art.

Agree with Jan. They're too small for anything functional. Patch, paint, move on.

That said, if you're a wine aficionado, they could make for some great floor to ceiling dry wine storage. Other than that, I don't think they're worth keeping.

How big is the condo? Do you lack storage? Do you have 4 seasons? If you're short on storage a series of shelves built to take storage cubes or baskets that fit perfectly can be 2 layers deep the back row used for seasonal or occasional use items or even bulky (skis skateboards ) stuff. if you have all the storage you need you really should drywall it. It's messy expensive and disruptive. usually 4 separate visit from pros.
so factoring the fuss of each solution a semi custom built in starts to sound better. I read all about tiny home living as they are super creative with any spare space. may help you with this dilemma. congrats on the new place!

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I would add in shelves and make it a bookcase