This butterfly that landed on a linden tree in front of me yesterday is a map (Araschnia levana), landkaartje in Dutch:
These butterflies have two generations a year; the one in the photo above is from the summer generation; a bit early, I think, but there you have it.
Strangely, the spring generation looks totally different:
No wonder people thought for a long time these were two separate species.
Here's a photo from the side, for the curious:
Thanks for watching!