Quake
Other people go on a holiday trip for fun and excitement, this geek just holds his ear to the wall and calls the firefighters on the resulting creaking. At 3 am this is by far the fastest way to get the company of approximately 10 metropolitan fire troopers (complete with helmets), 1 policeman and 1 policelady, all within a quarter of an hour, to visually check the house for cracks, take my name and depart asking me to closely watch the situation for visual changes ... I suppose this was the first tectonic activity I had the questionable pleasure of encountering in Vienna.
NB: The Hohe Warte Meteorologic Center offers earthquake infos and live seismic graphs, too - no clues though