Royal Observatory

The Royal Observatory stands on a hill in Greenwich Park, overlooking the River Thames in south-east London. It was founded in 1675 by King Charles II on the site of Greenwich Castle, a former Tudor hunting lodge. Sir Christopher Wren designed the first building, Flamsteed House, using materials from the old castle’s ruins. The hilltop position gave astronomers clear views of the sky and the river below. The observatory became the home of the Astronomer Royal, who led efforts to improve navigation and timekeeping. Its work helped shape Greenwich Mean Time, which became the world’s standard. The observatory played a key role in solving the problem of finding longitude at sea. In 1714, the Longitude Act created rewards for accurate navigation methods. Astronomer Royal Nevil Maskelyne began publishing *The Nautical Almanac* in 1767, using observations from Greenwich. The 28-inch Great Refractor telescope, installed in 1893, allowed detailed study of stars. Time signals, first dropped by a ball in 1833, were later sent by telegraph and radio. The Prime Meridian, passing through the site, was chosen as the world’s reference line in 1884. Visitors today find Flamsteed House, the original observatory building, filled with historic clocks and instruments. The Octagon Room still holds the 13-foot pendulum clocks donated by Sir Jonas Moore. The South Building houses later telescopes, including the 28-inch refractor. Outside, the hilltop offers wide views over London and the Thames. The site is part of Royal Museums Greenwich, alongside the National Maritime Museum and the clipper ship *Cutty Sark*. The Annie Maunder Astrographic Telescope, installed in 2018, continues research. The observatory’s legacy remains visible in its buildings, instruments and the meridian line marked on the ground.