I've made an enclosed garden with no outside door, entance only by spell. I used the pieces from the Winterhold entrance so there are open windows all around. I put it in an interior cell for now because there is no entrance to it from the outside and I wasn't sure where to place it. I wanted a view of surrounding trees mostly. The most out of the way places are mountainous and snowy which is not what I wanted. I prefer more sunny areas like riften. But in an interior cell I would have to make the surrounding landscape which seems like a lot of work. Advice? Should I keep in in the interior cell or find a spot in the Riften area or create a worldspace (which I've never done)?

Interior cells can be a lot less work than modeling a mini-world which has been done in some TES games.

If its doing what you want it to, you have done well.

Doors or teleport devices are good ways in and out.

I haven't done anything to the area outside the windows yet. It's all still greyspace. I haven't ever done any landscape building which is why I'm dithering over building a fake landscape outside my windows V.S. plopping the building into an already created landscape. How would you begin if you just wanted a fairly short view of trees? Where would you look for some encircling cliff/mountain pieces to enclose it? Any fake exteriors already in the game that I could copy and edit?