This was one of my first things I built.
The build has too many large spaces and definitely not a planned structure. It’s too squared and you might be thinking about interior walls and room designations. I would definitely plan a building out of the knowledge around architecture.
For room designations, think about if the building was a headquarters and what would be there and what would be necessary to properly naming it a HQ.
Everything looks flat and bland, the only colors I see are black,white, and brown. I would try adding greenery to the place to give it more color. Also inside there is a lot of open space especially in the storage room area. I would try giving the building more shape by adding a second floor and/or adding another square area off the side. I also noticed that the area leading up the entrance is barren with just the hedges on the side, perhaps add a fountain? Most of the walls and a few other things are smooth plastic I would try adding more materials and/or textures.
That is all I can think of, hope this helps in some way.
I would add more textures. Also a spy base would be kind of sci-if-ey with all their gadgets and stuff. Nice job on the exterior though!
Yeah the exterior was my favorite part of the build.