This 2nd century map by Ptolemy shows Austria, Croatia, Slovenia, and Switzerland.Ptomely was known as a writer, mathematician, geographer, astrologer, and astronomer. He published three major scientific treatises. The first, Almaghest, is the only known surviving ancient treatise on astronomy. The second, Geography, is a compilation of the Greco-Roman world. This second manuscript was used by Christopher Columbus on his voyage where he accidentally discovered the Americas.