Simplify the following text for a Grade 11 native English-speaking person.
Original: The Royal Observatory , Greenwich ( formerly the Royal Greenwich Observatory or RGO ) , in London , England played a major role in the history of astronomy and navigation , and is best known as the location of the prime meridian .
Simplified: The Royal Observatory , Greenwich ( Royal Greenwich Observatory or ` RGO ' ) was commissioned in 1675 by King Charles II .