You should be able to see through something set to 90% transparency, unless you're looking through multiple transparent objects and your ray trans limit is set too low (render>options). It could also be a strong specular highlight or reflection preventing your from seeing through.
You can exclude reflection via the compositing tag. In this case you would put the tag on the building you want to exclude from reflection and drag the building with the reflective material into the tag's Exclusion>Object box. The small icons to the right of the object you drag in the box control what's excluded, e.g. transparency, reflection, refraction, heirarchy.