See the home of the Prime Meridian of the World at London’s only planetarium. The Royal Observatory, Greenwich, located on a hill in Greenwich Park overlooking the Thames, played a major role in the history of astronomy and navigation. It was built in 1675 to help solve the riddle of longitude, which it did and was later designated as the Prime Meridian of the World and Greenwich Mean Time (GMT) became the universal measurement of standard time. In the Meridian Courtyard, visitors can stand with their feet straddling the western and eastern hemispheres.
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