It's the Hermannsdenkmal behind them.
Here is the Wiki info: Hermannsdenkmal - Wikipedia, the free encyclopedia
It's very difficult for me to understand this Sütterlinschrift, I can't recognise the first word. The last words: "... zum hermannsdenkmal um 13 Juni 1942"
The text says "Ausmarsch zum Hermannsdenkmal am 13. Juni 1942".
In the strict sense of the term, Ausmarsch means a "march out" (out of the barracks, out of the town, into the field etc.); but in this case it is probably best translated as "hike".