I had one. A big square one. My mom used to put me in it when we were outside in the yard and lay a sheet across the top to block some of the sun and keep the bugs off of me. XD It had those mesh sides, so the flies and stuff couldn't get in through those either.
I recall others having ones with the wooden bars, but that they were swiftly getting rid of them because of kids being strangled because they put their heads through the openings.
And then they changed how they folded up and killed a couple of babies. (
https://www.cpsc.gov/Recalls/2001/r...play-yardscribsbaby-trend-launches-new-effort <-Baby died in 2001 because they were using a product that was recalled in 1995.)
Mostly now you just see 'play yards', those little plastic fences that you can set up where-ever you like. The closest things I've seen to a play pen now are those tiny little travel 'cribs', that are both a crib and changing table. But they're really not big enough for much else.
If you want memories of what mine looked like, I don't recall much.
I think it was similar to this one:
Maybe not that exact color/pattern, but I know it was built like that. The sides could still collapse on those, too, but with the mesh sides the baby might not suffocate before they were found. The trouble is that the more mobile the baby is, the more they try to escape. And eventually they get too heavy to try and climb the side and the hinges fail and down goes baby, usually pitched forward onto their poor noggins. If they're not locked right, they can just give away from the baby pulling themselves up on them to walk around.
And that's probably why we don't see a lot of those types of playpens still around. It's safer and easier just to block off part of the room and keep an eye on them. (Well, technically you were supposed to be keeping an eye on them in the playpen, but there you are with the lazy parenting or even the honest "I just stepped out to make a bottle!" stuff.)