One of the delights of Czech cuisine are the many recipes made using poppyseeds. To feed the Czech appetite for "mak" you will find the Czech countryside covered with fields filled with poppies. They make a stunning show too, but alas a time-limited one. Unlike the sometimes equally remarkable display of wild poppies we have in England which can turn a field bright red, the Czech version is a pale lilac colour.
The reason is that these are opium poppies. In the old days Czechs would harvest some of the green poppy heads and set them aside for medicinal uses. I heard on Prague radio the other day that even eating too many Czech poppyseed cakes for breakfast can result in your blood testing positive for the narcotic. But don't let that stop you trying them, you have to eat at least six before it does so, and six is too much for even the most avid cake eater.