Where does the prime meridian exist on a world map?

Answer 1

From Wikipedia:

"The Prime Meridian, also known as the International Meridian or Greenwich Meridian, is the meridian (line of longitude) passing through the Royal Greenwich Observatory, Greenwich, England — it is the meridian at which longitude is defined to be 0 degrees. The prime meridian, and the opposite 180th meridian (at 180° longitude), which the International Date Line generally follows, separates the eastern and western hemispheres."

Check the link for more information -- hope this helps!

Answer 2

Find Greenwich, England. Draw a line from the north pole to the south pole, passing through that city. That's the prime meridian. Here's a picture: http://worldatlas.com/aatlas/newart/locator/meridian.htm

Even on a flat map it'll still be the same as on a globe.