I received this card from my penpal about 2 years ago. I've never been to Kalkar, but I know it's quite close to the Dutch border.
Kalkar is a municipality in the district of Kleve, in North Rhine-Westphalia, Germany. It is located near the Rhine, approx. 10 km south-east of Cleves. The most famous building of Kalkar is its church St. Nicolai, which has one of the most significant sacral inventory from the late Middle Ages in Europe.