I made a 3d model in Blender and showed it to an architect, with the huge caveat that I only work in vfx and games and have absolutely no idea how to build real things, so please just consider it a "napkin sketch". This model was just flat colors, I didn't bother with texture maps.

I also used QGIS to show him a map of the site, along with some LIDAR elevation data I downloaded from a government website. He just took elevation/plan images and did a great job translating it into a real set of drawings with some major improvements.

After that I took his drawings and did a 3d model in FreeCAD, to help determine where our existing furniture will fit before I broke my back moving it around.