Of my many old builds, this is one of my favorites, I even used it as part of my admin lair on an old server world. The Sky Base is pretty spacious and fancy! Because it floats in the sky, This could work well in both the overworld and possibly in the end as well, if you wanted to have yourself a nice base there. :)

.
Features:
-3 ways to get in/out of the sky base - a waterfall switch, a bridge/dock, and a nether portal.
-a bio-dome with plants and sheep
- a Jacuzzi
- a reading room
- a swimming pool
- shower room
- sleeping areas
- storage area
- bathroom
- lounge with pool table
- small scouting ship outside

As usual, you can use this for whatever you'd like, just please give me credit!