unlabeled QR code on trainstation Hallerstraße

Yesterday on my way to the cinema I took the subway and spotted a billboard while passing through the trainstation Hallerstraße. The billboard had nothing on it but a QR code on a plain white background. Not a single word, number, logo or anything. Naturally it arose my interest. So today I detoured myself on my way to uni to stop by the billboard again and took a photo:

Then I googled an online QR Code reader and checked it out.

Rather disappointing, though, I was hoping for more than just one simple link. Like a little riddle, a challenge and a scavenger hunt or something. But to not take the fun out of this I won't say anymore about it than feed the photo to the QR reader, check it out for yourself and maybe polish your German