Why was St. Petersburg founded?

St. Petersburg was founded by Peter the great in 1703 to protect the lands he had just conquered from Swedish forces.

During the course of the Northern war with Sweden, Russian forces defeated  Swedish forces  and conquered the lands in the Neva Delta. To protect  this  prize, Peter the great  needed a fortress.

So at the spot where the Neva river meets the gulf of Finland off the Baltic sea, on the 16th - May 1703, tzar Peter the great ordered the city be built, beginning with a fortress.

Soldiers and peasants were ordered  to build  the fortress under the careful supervision of  the tzar and his close associates. Due to the very damp climate and primitive conditions and long work hours, the workers died in great numbers but the work went on. By 1712, the city was big enough to become the new Russian capital.

answer(c) carved on a babylonian clay tablet that showed earth as a flat circular disk;

i'm sure the answer you are looking for would be

a. an ice age

hope this contact me if this didn't or you need with more answers : )