Prime Meridian

• The Prime Meridian is the Zero Parallel of Longitude based on Greenwich, London, in the United Kingdom. GMT means Greenwich Mean Time.
• The Greenwich Prime Meridian was adopted in 1884 as the world prime meridian by 22 countries at the International Meridian Conference in Washington D.C.

Roman Prime Meridian

• During the Roman Empire, the Roman Prime Meridian was based on Mount Teide, Tenerife, in the Canary Islands.

Prime Meridian Greenwich