Regards the rabbit holes being two stories and using basements. If you want to build just a single story rabbit hole, you will need to add a basement and stairs down, keeping space in front of the entrance to the rabbit hole free as that is of course how sims get to work. The great thing about Lunar Lakes rabbit holes is that they have only one entrance. There are no back or side entrances to keep clear. So only the front entrance needs to accessible.
I sometimes use that slanted green back as part of the look to the building. Here's an example:
https://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/060/266/30/l0wd_original.jpg
https://www.thesims3.com/assetDetail.html?assetId=6026630
It's a spa on that long stretch of beach:
https://lvlt.thesims3.com/sims3_asset/sims3_asset/thumb/shard000/000/060/266/30/l2wu_original.jpg
So, while it's a very different look, it's fun to play around with, I think.
