3. Royal Observatory Greenwich Founded as a scientific institution for navigational research by Charles II in 1675, the Royal Observatory is the home of the world's Prime Meridian - longitude 0° - and of Greenwich Mean Time. The clocks developed by John Harrison to determine longitude at sea are among the Observatory's most treasured possessions. Next door is the Peter Harrison Planetarium, a state-of-the-art facility housed in a contemporary new building.

4. The complex at Greenwich includes many edifices besides the observatory including the Meridian Building, Flamsteed House, the National Maritime Museum and the Queen’s house. Flamsteed House contains the apartments used through the centuries to house the Astronomer Royals and their families. It was also the first Greenwich Royal Observatory. In 1833, Flamsteed House made the news when a time ball was constructed on its roof. This time ball was designed to drop every day at precisely 1 p.m. GMT and has continued to do so for more than 150 years. Visitors to the complex can visit view galleries filled with displays showing the formation of the universe, a history of timekeeping, photographs taken of deep space, and other stunning exhibits. The Greenwich complex also features a cutting-edge planetarium. Astronomers Royal at the observatory study the heavens with a 28-inch refracting telescope, one of the largest in the world. In 1997, the Greenwich Royal Observatory was designated a UNESCO World Heritage Site due to the advancements it has made in mankind's understanding of the universe. These include the first sightings of Uranus and the predicted return of Halley's comet.