Actually, I have no real idea when this sticker was printed and sold or given away [now updated, see below ], but I believe the caption translates as “Naturally, Harz.”
The caption might seem a little cryptic, unless you imagine a sticker with a women wearing nothing but a ten-gallon hat, with the caption “Naturally Texas.” That is because the witch is from the Harz mountains naturally (i.e., obviously), she is a witch and witches congregate on The Brocken in the Harz mountains, just as ten-gallon hats breed on the heads of Texans. Or something.
The witch is also as naked. That is, she is “naked as nature intended”—she is a natural beauty—and she is presented in her natural state (remember that nudists were also called—and may still be called—naturists [not naturalists, though they may be naturalists too].)
The Brocken, and large parts of the Harz mountains for all I know, sells itself as a tourist destination because it is an area of natural beauty, like a nature reserve or national or state park. So, the caption seems to also be both a claim (the Harz mountains is an area of natural beauty) and an invitation (“Come to the Harz Mountains to enjoy nature”).
Combine these three and you see that we should all go to the Harz mountains, to see nature and naked witches, or to enjoy nature and naked witches. Or something. I swear I am not making this up!
[UPDATE 18 July 2011: As Twixraider comments, the typography, photography, makeup and poor colour separation suggest a date earlier than 2000—which is the date given to it by the person I bought it from. I have chosen the mid-point of “the late 1970’s or early 1980’s”: thanks Twix!]