Transit of Venus is a rare astronomical phenomenon happens only twice in century. Between 17th and 19th centuries the observations of the transit was a unique way to measure Earth-Sun distance and make the first realistic estimates of the size of the Solar System. The 9 December 1874 transit of Venus made many expeditions to locations around the globe including a German expedition to Isfahan, Iran, where they left these two stone markings from their successful observation. The photo shows the stones in 2004 in the yard of Vank cathedral, Isfahan.