The field of geometry was probably developed by several cultures over millennia, but only in crude, elementary forms. Some of the first to actually work with geometry were the cultures of the Mesopotamian region around 3500 B.C.E. (especially the Babylonians). They were the earliest peoples to know about what is now called the Pythagorean theorem (in fact, the Greek mathematician and philosopher Pythagoras of Samos [c. 582-c. 507 B.C.E.] may have actually learned about this theorem in his travels to the east), and they possessed all the theorems of plane geometry that the Greeks attributed to Thales. The Egyptians came next, using geometric methods mainly for construction of huge monuments. This included the sundry pyramids and monuments of the region, some of which still dot the landscape today—a tribute to their builders who used geometric techniques.
The Greek mathematician Pythagoras may have learned about the geometric principals that led to his famous theorem during his travels to such places as Babylon.