***Let me say first that I make NO safety recommendations on this and if you follow this project you do so at your own risk.***
One of the girls' favorite things on a playground is monkey bars. But most of the playgrounds closest to our home don't have them. So we built them in one of the girl's closets.
We fastened 2x4s to 3 walls of her closet and capped the front with a 4th piece. Electrical conduit is used to make the bars and we drilled holes into the 2x4s to hold them. Then we screwed down through the top of the 2x4 and into the bars to keep them from spinning as that would suck when trying to catch the next one. Originally we wrapped them with duct tape to soften it on her hands but we found she actually just preferred it as plain bars.
The girls have loved it but it wasn't very pretty to look at so I made some curtains for the outside of it. The same curtains that Luna ate a couple days ago. Last Thursday I was home with a sick kiddo so I made another curtain to replace it and got them hung up. Now it has a little reading corner inside when she isn't using it as monkey bars.
And the curtains can all close up to make a private fort as well.