Twitter user Julie Kiggins reveals this unique piece of furniture at the University of Wollongong in Australia. This bench has curved lines in the slats. But, Kiggins tells us, on the days of the summer and winter solstice, the angle of the sun is just right to turn their shadows into straight lines. Because Australia is in the southern hemisphere, its winter solstice is June 21 and its summer solstice is December 22.