A classic astrophotography subject, startrails can show how much the celestial sphere rotates in just a few hours (in this case, 4).
This one in particular also highlights how many airplanes wander above our heads, you can see lots of them quite clearly, straight intermittent lines striking the perfect circles drawn by the stars.
This simple yet effective tecnique also has the side effect of allowing to build a timelapse using the very same set of images.
Technical data: Canon EOS 700d, Tokina 11m-16mm (at 11mm, F/3.2). ISO 1600, exposure 3 seconds, I also used a star adventurer mini to get pinpoint stars, although with this focal length it might have been a bit of an overkill.