 Greeks also called it Hyrcanian/Hyrkanian Sea ().In the 18th century, during the rule of Peter I the Great, Fedor I. Soimonov, hydrographer and pioneering explorer of the Caspian Sea charted the until then little known body of water.Soimonov drew a set of four maps and wrote "Pilot of the Caspian Sea", the first report and modern maps of the Caspian, that were published in 1720 by the Russian Academy of Sciences.