The ancient Eratosthenes experiment concerning the earth's circumference offers the opportunity of an inquiry-based revival in today's science classrooms: A multinational European science education initiative (acronym: OSR) introduced this experiment as a hands-on basis to extract the required variables and to exchange results with classroom peers across two continents, including Finland in the North, via Poland and Serbia to Greece and Egypt in the South. The aims behind focused on typical science requirements in classroom approaches such as measurement spreads of scores, translation of one score into its context as well as to solve a complex scientific question with simple hands-on results when unveiling nature's hidden principles. Within the scope of this present study, 2180 students from 89 schools in 5 different countries (Finland, Poland, Serbia, Greece, Egypt) completed the Eratosthenes experiment on the same day. Working groups of up to four students collected the measurement scores within their school sites which by selection covered about 30 degrees of latitude. The analyses clearly show more accuracy in the scores as more distant the measurement sites are located (within Greece: 17.6% error; Greece-Finland: 1.3% error). Recommendations for school implementations as well as its potential in experimental science classrooms are discussed in detail.