OK, also cool! The Athanasius Kircher society website has a story on the Longest Running Scientific Experiment. Number three is the coolest one... well, cool is relative, right? A funnel full of pitch has been slowly dripping since 1927 - one drop every 8 or 9 years. There are others in the articles, and referenced in the comments. Pretty amazing. Seems like almost no one can think on this sort of time scale nowadays.