Caspian Sea
The wide and endorheic Caspian Sea has a north–south orientation and its main freshwater inflow, the Volga River, enters at the shallow north end. Two deep basins occupy its central and southern areas. These facts lead to horizontal differences in temperature, salinity, and ecology. The Caspian Sea spreads out over nearly 750 miles (1,200 km) from north to south, with an average width of 200 miles (320 km). It covers a region of around 149,200 square miles (386,400 square km)—bigger than the region of Japan—and its surface is about 90 feet (27 meters) below sea level. The sea bed in the southern part reaches as low as 1,023 m (3,356 ft) below sea level, which is the second lowest natural depression on earth after Lake Baikal (−1,180 m, −3,871 ft). The ancient inhabitants of its coast perceived the Caspian Sea as an ocean, probably because of its saltiness and large size.
Fedor Ivanovich Soimonov
Soimonov made the first thorough hydrographic survey of the Caspian Sea between 1719 and 1727, building up on the survey previously done by Karl Van Verden during tsar Peter the Great's drive for reform and modernization at the beginning of the 18th century. He led the Caspian Expedition that explored the coasts of the sea. As a result of the survey Soimonov drew a set of maps of the Caspian for the 'Atlas of the Caspian Sea' "(Atlas Kapiiskago Moria)" and wrote the 'Pilot of the Caspian Sea'. Published in 1731 by the Russian Academy of Sciences, these became the first comprehensive report and the first modern maps of the Caspian in history. Between 1730 and 1738 he was employed as a cartographer for the Russian Admiralty Board, which had been established in 1718 by Peter I the Great.