A prime meridian is an arbitrarily-chosen meridian in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian form a great circle. This great circle divides a spheroid, like Earth, into two hemispheres: the Eastern Hemisphere and the Western Hemisphere.
Greenwich Park
Greenwich Market
Cutty Sark
Royal Observatory Greenwich
Bill's Greenwich Restaurant
The Gipsy Moth
Goddards at Greenwich
Cutty Sark