This photo captures both the Renaissance castle ruins and the city of Heidelberg along the Neckar River below.

The only description on the back reads: Heidelberg – Schloß und Stadt. This translates directly as Heidelberg, Castle and City.
The poem on the front of the card translates as follows:
Old Heidelberg, you fine,
You city rich in honors,
On the Neckar and the Rhine,
No other comes right to you!
This card was used, and mailed from München, which allows it to be dated 22 June 1956.