Things that make you go...hmmm...

Wait a minute!
I just did some research. The belly button is one of your first scars, therefore, it's actually a scar. The belly button does look like a body part though.

Wait it actually is? Wow i thought it was a birthmark

's a scar.

A birthmark is a scar, XD!
I used to thought it was a body part. It's ironic ain't it.
The belly button is a scar.

Scars, I dont remember what I was looking for, but a bellybutton is defined as 'A SCAR that got got left behind after the umbilical cord was removed.'

Body features

If you mean the navel, then yes, it's officially a scar.
When you are still in your mother's belly as a fetus, your mother provides you food and oxygen through the navel cord, and the stuff you do longer need (bluntly said, your shit, piss and the air you'd otherwise breath out) leaves you through that same cord.

After your birth, the navel cord is removed and then the navel is the scar that remains, and medically it has from that moment on no more function at all.
The shape is a bit differently, as nature intended you to have this scar, and thus nature has a kind of system in how to form that properly, this contrary to a scar you get from a wound that you were not supposed to have, like after falling or after getting cut. So that's the reason a navel looks differently from a "normal scar", but still it is a scar.

I know a navel could look sexy, but I guess we find anything sexy when it comes to people we find attractive in general, as it has no sexual features, nor any other features at all.

I think body features, but i would ask a doctor for the real answer