And the concern with Geocachers is that they don't damage the sites either... they're just as keen for others to be able to fully enjoy them too.
Hence usually placing the cache slight further away from the area, but within view.
Can I suggest going on a cache hunt? You don't necessarily need a GPS, a map will do, and to pick a location of your choice. That way, you will see that caches do not infronge on heritage sites.