We have our secret experiments scattered all over the world in different facilities and they are mostly in the desert. Anyone would be crazy to even go look for them because they are deep underground and no access to them is available from the actual locations. We have far too many dangerous and powerful experiments being conducted in these areas and that is the main reason why we could never allow anyone to see them.
We are completely sure that if many of our experiments ever saw the light of day we could forever change humanity in a very negative way. People would probably become frightened if they found out certain things. It would be difficult to control the mass hysteria. We have experimented with humans in ways that even the most horrific movies have yet to depict and we have also created biological weapons beyond your wildest dreams.