The Andaman Islands! It's home to tribes like the Sentinelese and Jarawa, protected by law from outsiders getting within three miles of the place. The people are so untouched by modern life - including modern germs, diseases, etc - that someone visiting could literally destroy their ecosystem and wipe out all humanity there.
It's kind of sad, though, because people keep trying to visit the place, anyway. I'm not sure why humans feel a need to do that - do you?